Poster Presentation Abstracts:

Assembly, Gas Content and Star Formation History of Galaxies
The Fourth North American ALMA Science Center Conference

September 21 – 24, 2009
Omni Hotel, Charlottesville, Virginia.

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Elizabeth Adams
Cornell University

Identification and Detection of Compact High Velocity Clouds in the ALFALFA Survey

For over two decades now, the mismatch between the number of low mass halos predicted by dark matter simulations and the number of observed low mass galaxies has been recognized (e.g. Klypin et al. 1999). Much work has gone into resolving this discrepancy, both in finding missing low mass galaxies and explaining why low mass halos may not host luminous galaxies. Recently, a class of compact high velocity clouds (CHVCs) have been detected in the ALFALFA survey that are consistent with the interpretation that they are minihalos in the Local Group. A preliminary sample of these objects, identified manually, are described in Giovanelli et al. (2009, in prep). These objects do not violate $\Lambda$CDM halo scaling parameters and are of low enough mass ($\sim 10^{5}\,d_{Mpc}^{2} \, M_{\odot}$) that they would not have been detected by HI surveys of nearby galaxy groups other than the Local Group. Here, we present preliminary results from a signal extraction method designed to automatically detect these objects in data from the ALFALFA survey.


Kate Barnes
Indiana University

UV Colors of Star Forming Regions in the Outer Disks of Spiral Galaxies: the Effects of an Episodic Star Formation History

We have obtained deep FUV, NUV, and H$\alpha$ imaging of a small sample of nearby spiral galaxies in order to study the recent massive star formation in the outer disk. We have identified $\sim$20-60 individual star forming regions outside of R$_{25}$ for most of the galaxies in our sample. Similar to other studies, the UV colors of star forming regions in the outer disks show a large amount of scatter. We are able to reproduce the observed range of FUV-NUV colors using GALAXEV models with episodic sampling of exponentially declining star formation rates. We compare results for both the inner and outer disk; we find that the time between star formation episodes combined with the ratio of current to past star formation rate has a pronounced effect on the predicted range of FUV-NUV color. An episodic star formation history could occur if star formation in the outer disk is largely a stochastic phenomenon, or if it is self-regulated by stellar winds or SNe.


Sandipan Basu
Florida International University

The LITTLE THINGS Survey

The processes that lead to star formation on galactic scales are poorly understood even in the simplest systems in the universe, dwarf galaxies. At best we have incomplete knowledge of certain processes in certain environments. Here we present preliminary HI images of a small subset of galaxies from the LITTLE THINGS Survey: a complete dataset on a sample of 41 dIm galaxies chosen to span a range of luminosities. We are tracing their stellar populations, gas content, dynamics, and star formation indicators. We were granted over 300 hours of time with the VLA in B, C, and D array configurations to obtain deep HI-line maps of the sample with high angular and velocity resolution to combine with our optical, UV, and IR data to answer the following questions: 1) What regulates cloud/star formation in tiny galaxies? 2) How is star formation occurring in the outer parts of dwarf galaxies, where the gas is gravitationally stable? 3) What happens to the star formation process at breaks in the exponential stellar light profiles? 4) And, what is going on with Blue Compact Dwarfs? More information can be found at http://www.lowell.edu/users/dah/littlethings/. We gratefully acknowledge funding for this research from the National Science Foundation with grants to DAH (AST-0707563) and CES (AST-0707468).


Estelle Bayet
University College London

Are the 12CO lines good indicators of star-formation rates in galaxies?

Since late 90's, there has been a lot of work aiming at better describing and understanding the link existing between the reservoirs of molecular gas contained in galaxies and their activity of star-formation. Historically, this study started with the Schmidt-Kennicutt law and its parametrization on local galaxies which led to a power index of about 1.4. However, this relationship does not actually link the \textbf{mass} of the molecular gas, more useful quantity, with the star formation rate in galaxies. The last ten years researchers have thus investigated this problem using various tracers of molecular gas (CO(1-0), CO(3-2), HCN(1-0), HCN(3-2), etc...) and different conversion factors (e.g. CO-to-H$_{2}$ factor) providing unfortunately a partial answer. The subject of my talk is to present the first systematic and coherent study of the relationship existing between the CO lines luminosities and the star-formation rate as derived from infrared emission. For the first time, this relationship is studied over a large range of z (from 0 to 6) and over several (twelve) transitions of the same molecule (CO). This work thus provides to the community the most complete study to date on that topic, in terms of line and source samples investigated. I will present in my talk the slopes and the correlation coefficients defining these observational SFR-CO line luminosity relationships we have obtained. We show that the tightest relationship is found for the high-J CO lines (e.g. CO(6-5), CO(7-6)) making them better indicators of star-formation activity in galaxies than the lower-J CO lines (e.g. CO(1-0), CO(2-1)). These results are compared with the state-of-the-art modelling approaches using 3D non-LTE radiative transfer calculation with hydrodynamical simulation of isolated disk galaxies and galaxy mergers. We confirm observationally what has been inferred by these models that the key quantity to define such relationships is the critical line density as compared to the mean gas density of the studied environment. We however find discrepancies between the predicted and observed SFR-CO line luminosity relationships (slopes) for the high-J CO lines. Several explanations for such discrepancies have been investigated and will be also discussed in details in the talk. By the tools provided, this study is of particular interest for especially better understand more generally the formation of galaxies in the Universe, especially in the context of ALMA and Herschel.


Guillermo A. Blanc
University of Texas at Austin

The Spatially Resolved Star Formation Law from Integral Field Spectroscopy: VIRUS-P Observations of NGC 5194

I will present the first IFU measurement of the spatially resolved star formation law in nearby galaxies. VIRUS-P integral field spectroscopy of the central 4.1 kpc x 4.1 kpc of NGC 5194 (M51) is used to measure H$\alpha$, H$\beta$, [NII]$\lambda \lambda$6548,6584, and [SII]$\lambda \lambda$6717,6731 emission line fluxes for 735 regions $\sim$170 pc in diameter. We use the Balmer decrement to calculate nebular dust extinctions, and correct the observed fluxes in order to measure the SFR surface density in each region. HI 21cm and CO J=1-0 maps are used to measure the atomic and molecular gas surface densities. Line ratios are used to separate the contribution to the H$\alpha$ flux from the DIG and the HII regions in the disk. We present a new method for fitting the Star Formation Law (SFL), which includes the intrinsic scatter in the relation as a free parameter and allows the inclusion of non-detections in both SFR and gas surface densities. After removing the DIG contribution from the H$\alpha$ fluxes, we measure a slope $N=0.82\pm 0.05$ and an intrinsic scatter $\epsilon=0.43\pm 0.02$ dex for the molecular gas SFL. We also measure a typical depletion timescale $\tau=2$ Gyr, in good agreement with recent measurements by Bigiel et al. 2008. The disagreement with the previous measurement of a super-linear molecular SFL by Kennicutt et al. 2007 is most likely due to differences in the fitting method. Integral field spectroscopy allows a much cleaner measurement of H$\alpha$ emission line fluxes than narrow-band imaging, since it is free of the systematics introduced by continuum subtraction, underlying photospheric absorption, and contamination by the [NII] doublet. The data shows an excellent agreement with the recently proposed model of the SFL by Krumholz et al. 2009. The large intrinsic scatter observed implies the existence of other parameters, beyond the availability of gas, which are important at setting the SFR.


Charlotte Christensen
University of Washington

Molecular Hydrogen in Cosmological Simulations of Dwarf Galaxies

The structure and luminosity of dwarf galaxies are highly responsive to the amount of star formation (SF) and stellar feedback occurring during their evolution. This responsiveness makes dwarf galaxies a sensitive environment in which to test the connection between SF and the properties of the host galaxy's cold interstellar medium (ISM). To examine SF in dwarf galaxies, we include the non-equilibrium formation of molecular hydrogen in Smoothed-Particle Hydrodynamic cosmological simulations of galaxies. We calculate the distribution of molecular hydrogen, cold atomic hydrogen gas, and stars in our simulated galaxies and relate the spatial distribution of each. To judge the evolution of SF, we compare the star formation histories of our simulated galaxies to observations and track the fraction of time spent in bursts of SF.


Michelle Cluver
IPAC, Caltech

The Shocking Reality of Molecular Hydrogen Cooling in Stephans Quintet

Stephans Quintet is a strongly interacting compact group experiencing a group-wide shock due to the high velocity ($\sim$1000~km\,s$^{-1}$) collision of an intruder galaxy with the intragroup medium. Extremely strong, pure rotational H$_{2}$ emission was recently detected at the centre of the shock-excited filament seen at radio wavelengths. I shall present results from deep, mid-infrared spectral mapping of Stephans Quintet, using the {\it Spitzer Space Telescope}, that show for the first time the striking abundance and widespread distribution of warm H$_{2}$ and confirm the molecular hydrogen emission lines as the dominant cooling pathway in the shock. In the main shock region alone, we find 2.8~$\times$10$^{8}$\,M$_{\odot}$ of warm H$_{2}$ covering $\sim$480\,kpc$^2$. We additionally report the discovery of a second, major shock-excited feature, likely a remnant of previous tidal interactions, also producing strong pure rotational H$_{2}$ emission. This brings the total H$_{2}$ line luminosity of the group in excess of ${10}^{42}\, {\rm erg\, s^{-1}}$, exceeding the X-ray luminosity by a factor of $\ge$ 3. Correlations with other emission lines will be discussed, in particular the close association with $[$Si\,{\sc ii}$]$ and the lack of star formation (as traced via nebulae lines or PAH emission) in the main shock. The concordance with a model of H$_{2}$ emission driven by turbulent energy transfer, and the prevalence of this pathway over other sources of cooling in fast galaxy-scale shocks, may have important implications for the cooling of gas in the assembly of the first massive galaxies, as well as shock physics in systems ranging from ULIRGs to supernovae remnants


Genevieve de Messieres
University of Virginia

Spitzer Mid-Infrared Spectra of Cool-Core Galaxy Clusters

We present mid-infrared spectra of the central galaxies in nine massive cool-core X-ray clusters, obtained using the Infrared Spectrograph of the Spitzer Space Telescope. They display strong molecular hydrogen emission, which dominates the spectrum in some cases, but most have weak warm dust continua and PAH emission. With the exceptions of Abell 1068 and Abell 1835 (classic starbursts), the spectra are anomalous compared to normal star-forming galaxies even though most of our sample are known from optical/UV data to be active star-formers. The anomalies may be associated with star formation that occurs at the interface between relativistic jets and the inner cooling flows rather than in a dense disk.


Jacqueline Fischer
Naval Research Laboratory

Dust-Bounded ULIRGs? Model predictions for Infrared Spectroscopic Surveys

In preparation for Herschel, SPICA, and JWST mid- and far-infrared spectroscopic studies, we explore the suggestion that the effects of high ratios of impinging ionizing radiation density to particle density (i.e. high ionization parameters, {\it U}) are responsible for many of the infrared spectral properties of ultraluminous infrared galaxies (ULIRGs) such as the faintness of the infrared fine-structure line emission, including the well known ``[CII] deficit'', and their warm far-infrared colors. We present a theoretical study of the emergent line and continuum properties of a cloud exposed to an ionizing continuum characteristic of an Active Galactic Nucleus (AGN) or starburst, taking into account the ionized, atomic and molecular environments under conditions of pressure balance. For both starburst and AGN input spectral energy distributions, we calculate how the spectrum changes with variations in {\it U} and compare the trends found with data in the literature. Our calculations show that high {\it U} effects can explain the nearly order of magnitude drop in the [CII]158$\mu$m/FIR ratio observed with the ISO LWS in ULIRGs and other warm galactic nuclei with high IRAS F(60$\mu$m)/F(100$\mu$m) ratios. High {\it U} effects also produce increases in the [OI]63$\mu$m/[CII] ratio similar to the magnitude of the trends observed, a gradual decline in the [OIII]88$\mu$m/FIR and produce a reasonable fit to observations of the [NeV]14$\mu$m/FIR ratio in AGN. The effects on absorption in the far-infrared rotational lines of OH and water are also discussed.


Sebastian Haan
Spitzer Science Center, Caltech

GOALS NICMOS Imaging: The Nuclear Structure of (Ultra) Luminous-Infrared-Galaxies in the Nearby Universe

Here we present Hubble Space Telescope NICMOS H-band images for the 88 most luminous (U)LIRGs in the Great Observatories All-sky LIRG Survey (GOALS), which combines multiwavelength imaging and spectroscopic data from space (Spitzer, HST, GALEX, and Chandra) and ground-based telescopes. High-resolution near-infrared observations are mandatory to recover nuclear structure that is obscured by dust from view at optical wavelengths. We find that a large fraction of all galaxies in our sample possess double nuclei (35-45\%) or show evidence for multiple nuclei and intense star formation regions. Comparison with HST ACS B-band images suggests that half of these double nuclei or nuclear star-formation regions are not visible at short wavelengths due to dust obscuration, placing strong limitations on the ability to detect the true nuclear structures of luminous infrared galaxies at high-redshift. We will discuss the results of the HST near-infrared imaging, and their implications for estimates of the lifetimes of the LIRG phase.


Laura Hainline
University of Maryland

The Infrared Spectral Energy Distributions and the Infrared-Radio Correlation for Submillimeter-Selected Galaxies

We combine deep imaging at 24 and 70\,$\mu m$ with the MIPS instrument on the \emph{Spitzer Space Telescope} with submillimeter photometry of the largest sample of submillimeter-selected galaxies (SMGs) with spectroscopic redshifts to examine the infrared (IR) spectral energy distributions (SEDs) and the far-IR--radio correlation for SMGs. The \emph{Spitzer} data for our sample of $\sim 50$ SMGs constrain the Wien side of the IR SED peak, and thus are vital to determine the contribution of warm dust emission to the total infrared luminosity. The mid-IR data indicate that while the infrared SEDs of SMGs are non-uniform in shape, the majority of SMGs do not have dominant contributions to their total IR luminosity from warm dust, and confirm that the spectral energy distribution of the nearest ultraluminous IR galaxy, Arp\,220, is not representative of SMGs and thus is a poor template with which to predict properties of SMGs. We show with the largest sample of SMGs to date that SMGs follow a tight, nearly linear correlation between IR luminosity and radio luminosity, regardless of AGN/starburst spectral type. We directly compare the IR--radio correlation for high-$z$ SMGs to that of lower-luminosity, local, IRAS-selected star forming galaxies to show that the IR--radio relation for SMGs is consistent with the local relation.


George Heald
ASTRON

The Westerbork HALOGAS Survey

Accretion of cold gas onto galaxies is a crucial part of their evolution, and seems to be necessary to replenish material used up by star formation. Past observations of neutral hydrogen have made clear that a large quantity of cold gas is present in the outer parts of a handful of nearby galaxies. Careful consideration of the kinematics of such gas, and comparison with theoretical work, suggest that a fraction of this gas is in the process of accreting, and that much of the star formation rate can be maintained by the infall of this fresh gas. However, the properties of accreting gas seem to vary substantially among the few galaxies which have so far been observed to sufficient depth. It is not yet clear how many galaxies are presently accreting gas, and what the general properties of accreting gas in the local Universe are. To answer these questions, we have recently started an ambitious program at the Westerbork Synthesis Radio Telescope (WSRT) with the primary goal of characterizing the statistical properties of cold gas accretion through sensitive HI observations of 22 nearby galaxies. I will describe the Westerbork Hydrogen Accretion in Local Galaxies (HALOGAS) Survey, which is presently underway. I will also present the first results from our pilot program, and describe the complementarity between these observations and those to be made with future facilities in understanding the effect of gas accretion on galactic evolution.


Sukbum Hong
George Mason University

GALEX Observations of Star-Forming Dwarf Galaxies

We present GALEX observations of 86 star-forming dwarf galaxies. All galaxies are selected from the KPNO International Spectroscopic Survey when they exhibit detectable H$\alpha$ emission. This sample already possesses optical observations at B, V, and R band images as well as mid-infrared observations at 3.6, 4.5, 5.8, and 8.0 $\mu$m imaging from Spitzer. We examine the relationship between star- formation rates computed in the optical, mid-infrared, and UV as a probe of the difference in calibration of the measures and physical properties of the star-forming region including the age of the starburst and possible evidence of the removal of gas and dust from the star-forming regions.


Minjin Kim
NRAO

Coevolution of Black Holes and Host Galaxies in Nearby Type I AGNs

We present the M(BH)-L(bulge) relation of broad-line AGNs by analyzing a sample of 237 low-z (< 0.35) AGNs. We derive black hole mass from optical spectra assuming a spherical broad-line region, and bulge luminosity from detailed two-dimensional decomposition of archival optical HST images. We find that our sample roughly follows the M(BH)-L(bulge) relation of inactive galaxies, but the zero-point is offset by ~0.5 dex toward lower BH mass and the slope is marginally steeper than inactive galaxies. We show that Eddington ratio dominantly give rise to the systematic offset to the \mlb\ relation. At a given bulge luminosity, sources with higher Eddington ratios have lower M(BH). The zero point offset can be explained by a change in the normalization of the virial product used to estimate M(BH), in conjunction with modest BH growth (~10%-40%) during the AGN phase.


Hannah Krug
University of Maryland

Neutral Gas Outflows and Inflows in Infrared-Faint Seyfert Galaxies

Previous studies of the NaI~D~interstellar absorption line doublet have shown that galactic winds occur in most galaxies with high infrared luminosities. However, in infrared-bright composite systems where a starburst coexists with an active galactic nucleus (AGN), it is unclear whether the starburst, the AGN, or both are driving the outflows. The present paper describes the results from a search for outflows in 35 infrared-faint Seyferts with L$_{\mathrm{IR}}$ $<$ 10$^{11}$ $L_{\odot}$, or, equivalently, star formation rates (SFR) below 10 M$_{\odot}$, to attempt to isolate the source of the outflow. We find that the outflow detection rates for the infrared-faint Seyfert 1s (6\%) and Seyfert 2s (18\%) are lower than previously reported for infrared-luminous Seyfert 1s (50\%) and Seyfert 2s (45\%). The outflow kinematics of infrared-faint and infrared-bright Seyfert 2 galaxies resemble those of starburst galaxies, while the outflow velocities in Seyfert 1 galaxies are significantly larger. Taken together, these results suggest that the AGN does not play a significant role in driving the outflows in most infrared-faint and infrared-bright systems, except the high-velocity outflows seen in Seyfert 1 galaxies. Another striking result of this study is the high rate of detection of inflows in infrared-faint galaxies (39\% of Seyfert 1s, 35\% of Seyfert 2s), significantly larger than in infrared-luminous Seyferts (15\%). This inflow may be contributing to the feeding of the AGN in these galaxies, and potentially provides more than enough material to power the observed nuclear activity over typical AGN lifetimes.


Peter Kurczynski
Rutgers University

Panchromatic SEDs of High-redshift Star-forming Galaxies

We present and analyze the rest-UV-through-radio Spectral Energy Distributions (SEDs) of high-redshift galaxies in the Extended Chandra Deep Field-South. Galaxies are separated into sets by their selection method (Lyman break, Lyman alpha emission, blue rest-UV colors) and into bins of photometric redshift. In order to obtain panchromatic SEDs for each set of galaxies, we performed stacking analyses in Spitzer-MIPS (24, 70 micron), sub-mm (870 microns from the Laboca ECDF-S Sub-mm Survey, LESS), and radio (VLA 1.4 GHz and GMRT 610 MHz).   We describe our stacking methods, including an optimized treatment of the deblending of multiple galaxy types in the sub-mm imaging.  The resulting SEDs are compared with low-redshift templates of galaxies with a variety of star-forming and AGN properties.


Glen Langston
NRAO

HVCs: Last Remnants of Galaxy interactions

I will present the most recent results from my Green Bank Telescope HI observations of nearby groups of galaxies. These observations are a search for HI clouds in the galaxy groups and along filaments between groups. This study will constrain models of the High Velocity Clouds (HVCs) that surround the Milky Way. By observing galaxy groups that span the range of interaction and merger activity, we explore the contribution of galaxy interactions to the HVC/HI cloud phenomenon. Additionally, I will present results from numerical simulations of galaxy groups which show the generation of cloud-like structures by galaxy interactions.


James Lowenthal
Smith College

Extreme starbursts: Spitzer Imaging of luminous blue compact galaxies at $z<$1

Luminous compact blue galaxies (LCBG) at redshifts $z<$1 are excellent analogs to Lyman break galaxies (LBGs) at $z>$2: they are small and low-mass but very luminous systems containing extreme starbursts and showing diverse morphologies. We have obtained Spitzer IRAC and MIPS images of 26 LCBGs, half at $z\sim$0 and half at $z\sim$0.5, to measure any dust-enshrouded star formation as a function of dynamical mass and rest-UV size and morphology. We also estimate the galaxies' stellar masses and compare their SEDs to those of both local field galaxies and distant LBGs as we strive to understand the role LCBGs play in overall galaxy evolution.


Joseph Mazzarella
Caltech

Dual AGNs, Outflow/Feedback, Large-Scale Shocks, and Super Star Clusters in the LIRG Mrk 266

Mrk 266 (NGC 5256) is a Luminous Infrared Galaxy (LIRG, $L_{ir}=10^{11.5} L_\odot$) involving a major merger between two gas-rich disks. Recent imaging and spectroscopic observations are presented from Spitzer, HST, GALEX, Chandra, and XMM, most of which were acquired by the Great Observatories All-Sky LIRG Survey (GOALS). The data reveal new evidence for gaseous outflow/feedback ranging from 0.2 kpc (inside the NLR) to 20 kpc (a galactic scale superwind), previously unknown properties of shock-excited gas concentrated between the colliding disks and dispersed throughout the superwind, and $\sim$100 super star clusters and associations. I will discuss these new results in the context of merging spiral galaxies evolving through luminous and ultraluminous infrared phases that involve large-scale winds, shocks and AGN ejecta that can dramatically alter the ISM. Being one of just a few (U)LIRGs in the local universe with confirmed high-luminosity, dual AGNs, Mrk 266 also has a lot to teach us regarding the origin of supermassive binary blackholes observed (or suspected) in some quasars and powerful radio galaxies.


Jesse Miner
UNC-Chapel Hill

A new NIR chronometer with application to high redshift galaxies

New and future space observatories, such as the Herschel Space Observatory and the James Webb Space Telescope, will offer astronomers unprecedented access to rest-frame infrared light from the first generation of galaxies. This is especially exciting because recent advances in the treatment of stars on the Thermally-Pulsing Asymptotic Giant Branch (TP-AGB) in stellar population models have indicated that there are unique infrared spectroscopic features in young ($\sim$100 Myr) and intermediate age ($\sim$1 Gyr) stellar populations. We will present ongoing work to calibrate these age-sensitive features with optical and near-infrared spectroscopic studies of nearby galaxies in order to develop an age-dating technique applicable to high redshift objects. Our approach is as follows: we obtain both optical and infrared spectroscopy of a sample of galaxies and use established optical techniques to determine the age and composition of the underlying stellar populations, and also measure the IR features predicted by recent models. The results from the optical measurements will be used to calibrate the IR features, in order to develop a NIR chronometer which will be particularly sensitive to galaxies with intermediate age stellar populations, thus making it particularly relevant for high redshift objects. The calibration is necessary because the features are due to contribution from evolved stars, whose fundamental properties are not well understood, and it will be a useful test of the predictive power of the new stellar population models. Our first thoroughly-studied object is NGC 5102, which has both a very young and an intermediate age stellar component, and thus will contain a large population of TP-AGB stars. Age measurements from optical spectroscopy of NGC 5102, and the predicted NIR features will be discussed.


Amanda Moffett
University of North Carolina

Extended Light in E/S0 Galaxies and Implications for Disk Rebirth

The recent discovery of extended ultraviolet (XUV) disks around ordinary disk galaxies provides evidence for disk building at recent epochs. Combining GALEX UV observations with Spitzer IR and deep optical imaging, we search for XUV disks in a sample of nearby low-to-intermediate mass E/S0 galaxies to explore evidence for disk rebuilding after mergers. Preliminary visual classification yields ten XUV-disk candidates from the full sample of 30, intriguingly similar to the late type fraction of $\sim$30\%. These XUV candidates occur at a wide range of masses and on both the red and blue sequences in color vs. stellar mass, indicating a possible association with processes like gas accretion and/or galaxy interactions that would affect the galaxy population broadly. We go on to apply the quantitative Type 1 and Type 2 XUV-disk definitions to a subsample analyzed in detail. In this possibly non-representative subsample, we identify multiple Type 1 XUVs, i.e. galaxies with UV structure beyond the expected star formation threshold. We also find several galaxies that come close to satisfying the Type 2 definition, but it proves problematic to apply to this sample: the NUV-derived star formation threshold radii for our E/S0s often lie inside the 80\% Ks-band light radii K80, violating an implicit assumption of the Type 2 definition, or lie outside but not as far as the definition requires. Nonetheless, we find otherwise Type 2-like galaxies that have higher star formation rates and bluer FUV - NUV colors than Type 1 XUVs in the sample, perhaps reflecting inside-out disk regrowth.


Sean Moran
Johns Hopkins University

Tracing Star Formation, HI Content, and Dynamics Across the Green Valley: Resolved Spectroscopy of Galaxies in GASS, the GALEX-Arecibo-SDSS Survey

We present initial results from our campaign to acquire longslit spectroscopy of galaxies in GASS, an Arecibo HI survey aiming to measure the gas content of a volume-limited sample of 1000 galaxies in the range 0.025$<$z$<$0.05. The GASS sample spans the critical `transition' mass separating star forming galaxies from passive red sequence galaxies. Earlier SDSS fiber spectra cover only the central few kpc of galaxies at these redshifts, and so provide no insight into the current and recent star formation histories of outer disks, where most star formation and most of the gas resides. Therefore, we have been pursuing a followup campaign of resolved longslit spectroscopy in order to make progress in relating these galaxies' recent star formation histories and internal dynamics to their total HI content. We trace these quantities to beyond one scale length in each galaxy, and our initial results uncover a number of peculiar cases of both HI deficient galaxies with extended ongoing star formation and seemingly quiescent red-sequence galaxies with copious HI. A statistically significant number of galaxies in the green valley fall into one of these two categories, and we will discuss the implications for the frequency and mechanisms of quenching or revival of star formation across the blue/red divide.


Juergen Ott
NRAO

Bridging Local and Global Scales: Molecular Cloud and Star Formation in the Magellanic Clouds

The Magellanic Clouds are the first milestone to understand molecular cloud and star formation on galaxy-wide scales. The Large Magellanic Cloud (LMC) exhibits an inclination that allows the detailed distribution of the giant molecular clouds (GMCs) while retaining the kinematic information (in contrast to the Galaxy). The Magellanic System is also close enough to identify all individual GMCs and thus provide enough objects to derive the statistical properties of their populations. We present CO observations with a resolution of 10pc of all GMCs in the LMC and deep observations of GMCs in the Small Magellanic Cloud (SMC). In addition, we will show interferometric observations of high density tracers (HCN, HCO+) towards a number of individual star forming regions at 2 pc resolution. We find that a simple column density argument is not sufficient for the transformation of atomic into molecular gas. It also appears that the radiation field that surrounds the molecular material only has little influence on most of the properties and thus the star formation abilities of individual GMCs. A trend, however, between the radiation field and the surface density of molecular material may exist. With the molecular gas being decoupled from the pressure equilibrium of their surroundings, the problem of star formation turns into a problem of molecular cloud formation. We will show how the GMC formation may depend on the global structure of a galaxy. Given the low metallicities of the Magellanic Clouds, our studies may have immediate impact in the understanding of 'normal' galaxies at high redshift. With their southern location, and their proximity that connects Galactic and extragalactic studies, the Magellanic System will be a prime target for future ALMA experiments.


Kyle Penner
University of Arizona

Gas in Disk Galaxies on the Fundamental Manifold

The Fundamental Manifold unifies the Tully-Fisher and Fundamental Plane scaling relations. The only galaxies found to deviate from the manifold are gas rich galaxies. We investigate the nature of these deviations using HI masses for a broad sample of local galaxies. Our goal is to recast the Fundamental Manifold in a form that is valid for all galaxies, and by doing so, gain some structural understanding of how galaxies convert their gas into stars.


D.J. Pisano
West Virginia University

The evolution of luminous compact blue galaxies: disks or spheroids?

Luminous compact blue galaxies (LCBGs) are a diverse class of galaxies characterized by high luminosities, blue colors, and high surface brightness. While they were relatively common at a redshift of one, and contribute a significant fraction to the star formation rate density at the time, they are a factor of ten rarer today and contribute negligibly to the current star formation rate density. As such, they are one of the most rapidly evolving populations of galaxies in the Universe. Given their location at the high luminosity, high mass end (halo masses less than $10^{12}$ solar masses) of the blue sequence, LCBGs sit at the critical juncture of galaxies that are evolving from the blue to the red sequence. However, we do not yet understand how these galaxies evolve nor their end products. To start answering these questions, we are conducting a multi-wavelength survey of rare, local LCBGs selected from the SDSS to be analogous to the common, distant LCBGs. We will present the results from single-dish and interferometic HI observations of local LCBGs and their implications for the evolution of local and distant LCBGs. Our data show that LCBGs have a diverse range of HI properties. They are characterized by HI masses similar to the Milky Way and dynamical masses similar to M33, yet they have gas depletion timescales of less than 2 Gyr. This is consistent with LCBGs evolving into low-mass spiral galaxies or high-mass dwarf ellipticals. However, despite the presence of large amounts of HI and signatures of normal rotation, LCBGs do not follow the Tully-Fisher relation. Furthermore, HI maps of many LCBGs show signatures of recent interactions and dynamically hot components, suggesting that we are seeing the formation of a thick disk or spheroid in at least some LCBGs. Finally, combined with optical spectroscopy, these data suggest that star formation in LCBGs is primarily quenched by virial heating, consistent with model predictions.


Nurur Rahman
Dept of Astronomy, University of Maryland

Resolved Star Formation Law in NGC 4254

An accurate knowledge of star formation law is crucial to make progress in understanding galaxy formation and evolution. We are studying this topic using CARMA STING (Survey Toward Infrared-bright Nearby Galaxies), an interferometric CO survey of a sample of 27 star-forming nearby galaxies with a wealth of multi-wavelength data designed to study star formation in environments throughout the blue sequence at sub-kpc scales. We will present results for NGC 4254 (M99), one of our sample galaxies. We construct star formation rate surface density (SFRSD) and gas (atomic and molecular) surface density indicators using a combination of high resolution data from KPNO, Spitzer, IRAM, CARMA, and VLA.


Richard Rand
University of New Mexico

A Spitzer Spectroscopic View of Galaxy Halos

Optical emission line ratios have provided much information on the ionization and energetics of gaseous halos. However, their interpretation is complicated by temperature, abundance and extinction variation. The Spitzer Space Telescope allows measurement of the infrared [Ne III]/[Ne II] ratio, which is essentially free of these complications and provides a straightforward measure of halo radiation field hardness. We report such measurements for the halos of the edge-ons NGC 891, NGC 5775 and NGC 3044. In the first two cases, optical line ratios cannot be explained simply by ionizing radiation leaking out of the disk. The neon ratio is higher in the halo than in the disk in both galaxies, presenting further serious problems for pure photo-ionization models. Scatter in the disk values for NGC 3044 prevent firm conclusions from being drawn. The spectra also allow PAHs in the halos to be studied. In NGC 891 and NGC 5775, scale heights for PAH features in the 10-20 micron range are comparable to those of the main HI layers. In NGC 891, the 8 micron scale height is significantly lower, suggesting a drop in PAH ionization with height. For all three galaxies, most equivalent widths are higher in the halos, suggesting a subtle change in the PAH population.


Amy Reines
UVa

A New View of the Super Star Clusters in the Low-Metallicity Galaxy SBS 0335-052

We have conducted a detailed multi-wavelength study of the individual super star clusters (SSCs) in SBS 0335-052, a blue compact dwarf galaxy well-known for its extremely low oxygen abundance and high star formation rate. New near-IR and archival optical HST observations, as well as radio continuum measurements from the VLA, are used to probe the stellar populations and the gaseous and dusty birth cocoons of the infant SSCs. The primary goal of this study is to investigate SSC formation and early evolution in an environment similar to that which might be found in primordial galaxies during the time ancient globular clusters were prolifically formed throughout the universe.


Jane Rigby
Carnegie Observatories

Lensed star-forming galaxies at 1$<$z$<$3

Much of the Universe's stars formed in major starbursts at 1$<$z$<$3. At present, detailed spectroscopy can only be obtained for rare starbursts that have been gravitationally lensed. Spitzer spectroscopy of 15 such lensed galaxies illustrates that the spectra have evolved dramatically between z=0 and z=2. This result has important consequences for star formation rate calibrations. Moreover, the spectral evolution strongly suggests that star formation at high redshift was not as heavily obscured as in local analogues, the z=0 ultraluminous infrared galaxies (ULIRGs). As such, z=0 ULIRGs may be misleading examples of how starbursts worked at high redshift. Another way to probe the detailed workings of high redshift starbursts is through rest-UV spectroscopy. I will present new Magellan spectra that probe the stellar populations, interstellar media, and outflows of average star-forming galaxies at z=2-3. At present, only strongly-amplified galaxies are bright enough for this work. JWST and twenty-meter optical telescopes will extend these studies to large samples of unlensed field galaxies, and ALMA will reveal how gas is driven in to fuel these starbursts.


Joel Roediger
Queens University

The History of Stellar Mass Assembly in the Virgo Cluster

Through a combination of optical and deep, near-infrared photometry for a statistically-complete sample of Virgo cluster galaxies, we have achieved an ideal laboratory for the simultaneous study of stellar populations across the multi-dimensional spectrum of galaxian parameter space. We use the evolution models of Bruzual & Charlot (2003) to determine best-fit mean ages and metallicities for the stars in these galaxies. The properties of the stellar populations which we determine are compared against galaxies of different types/concentrations, various galaxian parameters (e.g. V$_{circ}$) and cluster-centric position to better understand what controls star formation and chemical evolution in the cluster environment. Searching for such correlations also provides constraints in the development of a global picture of the formation and evolution of galaxies of different types. We also present preliminary efforts towards building 2D age/metallicity maps for the galaxies in our sample, which will offer a more complete picture of galaxy evolution, particularly with respect to environmental effects.


Jessica Rosenberg
George Mason University

Current and Future Observations of Star-Forming Dwarf Galaxies

Star forming dwarf galaxies are low luminosity systems that exhibit significant amounts of star-formation indicated by their H$\alpha$ emission. We have studied the mid-infrared and UV properties of a sample of these systems selected from the KPNO International Spectroscopic Survey. This sample is complete and has a well defined selection function that allows us to determine the space and luminosity densities of these objects including their contribution to the star formation rate density and the 8 micron luminosity density. I will discuss these observations and what they tell us about these galaxies which have some of the lowest metallicities in the local universe. In addition, these systems may share properties with a class of infrared faint Lyman Break galaxies at higher redshift. Observations with ALMA, Herschel, and JWST promise to teach us more about these galaxies at low redshift and probe their connection with galaxy populations in the more distant universe.


Barry Rothberg
Naval Research Laboratory

Dynamical Discrepancies in LIRGs/ULIRGs: Anemic Galaxies or Misrepresented Populations?

A key goal in astrophysics is the ability to identify the progenitors of present-day galaxies and their transformative processes. Mergers in the local universe present a unique opportunity for studying these metamorphoses in detail. Yet, many studies and simulations show gas-rich mergers do not contribute significantly to the overall star-formation rate and total mass function of galaxies. The ultimate implication is that $\Lambda$-CDM and our current understanding of galaxy formation and evolution may be completely wrong. I will discuss recent results, based on high-resolution imaging and multi-wavelength spectroscopy, which demonstrate how star-formation and the presence of multiple stellar populations has lead to a serious underestimation of the dynamical masses of star-forming galaxies, in particular, Luminous and Ultraluminous Infrared Galaxies. The dominance of Red Supergiants and Asymptotic Giant Branch stars in the near-infrared bands, where dust obscuration does not block their signatures, can severely bias the global properties measured in a galaxy, including: mass, age, extinction, and star-formation rate. I will also discuss the impact of these stellar populations on studies of high redshift galaxies.


Kurt Soto
University of California Santa Barbara

Stellar Population Gradients in Ultra Luminous Infrared Galaxies: Estimating the Merger Driven Gas Depletion Time Scale

Optical spectroscopy using the echellete spectrograph and imager (ESI) on Keck II are presented for nearby major mergers of gas-rich galaxies. These Ultra Luminous Infrared Galaxy spectra show strong A star features and H$\alpha$ emission, indicating recent starburst activity. We find that the strength of the H$\beta$ absorption line increases with the projected distance from the center of the merger. We interpret this H$\beta$ equivalent width as a measure of the time since star formation was suppressed, indicating older populations in the outer regions of the merger remnant. The time since truncation of star formation in the outer regions increases in each object, while star formation in the central kpc is consistent with continuous star formation. We interpret this result as evidence that gas depletion occurs first in the outer disk, likely due to merger-induced gas inflow. Our empirical constraint on the gas inflow timescale is central to modeling merger-induced star formation and AGN activity. Theoretical models accurately predict the total amount of infalling gas but simply guess the timescale.


Henrik Spoon
Cornell University

Mid-IR kinematic evidence for outflows in ULIRGs

We report on the results of a first systematic study of the line profiles of the mid-infrared fine-structure lines of Ne+, Ne2+, Ne4+ and Ne5+ (21-127 eV) in a sample of 200 ULIRGs, HyLIRGs, Seyferts, QSOs and starburst galaxies observed in the high-resolution mode (R=600) of Spitzer-IRS. The sources span a range of 5 decades in [Ne V] AGN luminosity and 6 decades in 21cm radio luminosity. We detect resolved line emission in the majority of ULIRGs, most notably in those with an optical Seyfert classification. Comparison of the velocity line profiles of different ionization stages indicates a gradual increase of ionization with increasing blue shift for part of our sample, whereas for other sources all neon lines have similar profiles. We further find a correlation between the FW20 and the line luminosity for the [Ne III] and [Ne V] lines. ULIRGs, the radio-loud ones especially, appear to form the high-luminosity end of this correlation.


David Stark
University of North Carolina, Chapel Hill

Gas-Dominated Galaxies and the Baryonic Tully-Fisher Relation

Gas-rich galaxies can be extremely useful tools in understanding galaxy structure and evolution. I will show results of a recent study where we calibrated the Baryonic Tully-Fisher (BTF) relation using a sample of gas dominated galaxies. These can determine the absolute scale of the baryonic mass--rotation speed relation independent of the choice of stellar mass estimator. Using gas masses derived solely from HI, we find a BTF relation consistent with several past studies that used primarily star-dominated galaxies. This approach can be used to put an independent constraint on the stellar mass zero point in population synthesis models. However, as the zero point remains uncertain, H$_2$ measurements are necessary to refine this method. IRAM, and soon ALMA, will put better constraints on the total gas mass of these galaxies. Further, recent dynamical studies of gas-rich galaxies have revealed the potential presence of missing baryons in extremely blue galaxies, possibly in the form of WHIM or ultra-cold molecular hydrogen. Constraining this additional component will also be important in obtaining the most accurate calibration of the BTF relation possible from gas dominated galaxies. Finally, the arrival of ALMA and the EVLA will allow the extension of this approach to gas dominated galaxies at higher redshift, building on pioneering studies of the CO Tully-Fisher relation.


Sabrina Stierwalt
Spitzer Science Center, Caltech

An HI-selected Sample of Low-mass Dwarf Galaxies in the Nearby Leo I Group

In 20\% of its intended coverage, the ongoing, blind HI survey ALFALFA has already made $>$300 detections with log(MHI)$<$8.0, many of which are very low surface brightness and were previously uncatalogued. Due to superior sensitivity and spectral resolution, ALFALFA is dramatically increasing the number of known dwarf galaxies in the local universe and probes the low-mass end of the HI mass function (HIMF) for the dwarf systems believed to be the building blocks of galaxy formation. At $\sim$10.5 Mpc, the Leo I group presents a nearby group environment well-suited for finding the lowest mass galaxies detectable outside of the Local Group. Although optical surveys find the Leo I environment lacking in dwarf galaxies, we derive from the complete ALFALFA sample in Leo I the only HIMF to date dominated by low-mass systems with 45 galaxies of log(MHI)$<$8.0, and compare with HIMFs previously derived for other nearby groups. However, we still find a shallower low-mass slope than that predicted by simulations of dark matter halo formation which suggests a population of gas- rich, low surface brightness galaxies does not solve the discrepancy between simulations and observations. Leo I is characterized by a low velocity dispersion ($\sim$175 km/s) despite the presence of E/S0 galaxies more typical of dense clusters. The group's proximity and intermediate density offer a unique basis for comparison of observed trends among Local Group dwarfs that offer key information to our understanding of dwarf galaxy evolution. An investigation of such trends, like morphological segregation and the dwarf galaxy metallicity-luminosity relation for the HI-selected gas-rich, yet still very low-mass dwarfs of the Leo I group will be presented. We will also discuss the potential of the ALFALFA survey as a whole for identifying tidal dwarf galaxies and for determining their contribution to the number of dwarfs observed at the current epoch as evidenced by our findings in Leo I.


Adrienne Stilp
University of Washington

Rolling Back the Clock: Star Formation and the ISM over Timescales of 1 Gyr

The interplay of star formation and the ISM is critical for shaping the baryonic component of galaxies. However, most current studies focus on studying only part of the ISM-star formation feedback cycle, and are concerned primarily with how the current properties of the ISM are connected to the current star formation rate. Equally important, however, is how the present state of the ISM has been shaped by past star formation. Recent episodes of star formation can potentially alter the kinematics and phase of the ISM, while leaving few traces in commonly used star formation indicators (H$_{\alpha}$, FUV, etc). Thankfully, HST gives us the means to accurately constrain recent star formation histories on timescales up to 1 Gyr, using CMDs of individual stars imaged at high angular resolution. We have obtained VLA multi-configuration observations in an NRAO Large VLA program (VLA-ANGST, PI = Ott) for a volume-limited sample of galaxies within 4 Mpc that also has extensive HST imaging from the ACS Nearby Galaxy Survey Treasury (ANGST). The combination of ANGST/HST and VLA data allows us to understand the impact of star formation on the ISM, including the triggering of star formation, the feedback of massive stars, and the energy budget of of the ISM on local and galaxy scales. I will present an overview of the current state of the survey, as well as preliminary results on the correlation between the star formation history and the velocity dispersion in select galaxies.


Jason Surace
Spitzer Science Center/Caltech

The Optical Morphology of Luminous Infrared Galaxies at z$\sim$0 and z$\sim$1

Luminous and Ultraluminous Infrared Galaxies are host to extreme star formation and are commonly invoked as models of galaxy formation. Their optical structure provides clues as to their dynamical state and the distribution of star formation within them. We discuss here comparative morphology derived from the GOALS survey (at redshift near zero) and the COSMOS survey (near redshift 1), and associated implications for the formation of these systems.


Stephanie Tonnesen
Columbia University

The Tail of the Stripped Gas that Cooled: Observational Signatures of Ram Pressure Stripping

Galaxies moving through the intracluster medium of a cluster of galaxies can lose gas via ram pressure stripping. This stripped gas forms a tail behind the galaxy which is potentially observable. We carry out hydrodynamical simulations of a galaxy undergoing stripping with a focus on the gas properties in the wake and their observational signatures. We include radiative cooling in an adaptive hydrocode in order to investigate the impact of a clumpy, multi-phase interstellar medium. We find that including cooling results in very different morphologies for the gas in the tail, with a much wider range of temperatures and densities. The tail is significantly narrower in runs with radiative cooling, in agreement with observed wakes. In addition, we make detailed predictions of HI, H$\alpha$ and X-ray emission for the wake, showing that we generally expect detectable HI and H$\alpha$ signatures, but no observable X-ray emission (at least for our chosen ram-pressure strength and ICM conditions).


Tomoka Tosaki
Joetsu University of Education

ASTE Dense gas Imaging of Star-forming galaxies(ADIoS)

We present recent results of ``ASTE Dense gas Imaging of Star-forming galaxies(ADIoS)". Dense molecular gas is one of essential components for star formation in galaxies. In order to understand the global distribution of a dense molecular gas in galaxies, we have conducted an extragalactic CO(3-2) imaging survey of nearby star forming galaxies using the Atacama Submillimeter Telescope Experiment (ASTE). For now, the targets of our survey are nine (or ten) galaxies; the local group galaxies (M31, M33, NGC 6822), nearby active galaxies (M83, NGC 253, NGC 986, Cen A, NGC 1365) and interacting galaxies (NGC 4567/4568). NGC 6822, one of the target of the survey, is dwarf irregular galaxy in the local group, and includes several star forming regions. Individual GMCs in the galaxy can be resolved, since ASTE beamsize, 22 arcsec, corresponds to 20 pc, which is smaller than the typical size of the Galactic GMCs. We observed three GMCs in NGC 6822, which show different activity of star formation. Each GMC show different CO(3-2)/CO(1-0) ratio and the GMC with higher CO(3-2)/CO(1-0) ratio shows more active and/or more evolved in star formation. Based on these results, we will discuss a CO(3-2)/CO(1-0) ratio as indicators of dense gas fraction and/or evolutional stages along star formation.


Sarah Tuttle
Columbia University

First Results from FIREBall: Searching for the CGM using emission

FIREBall (Faint Intergalactic Redshifted Emission Balloon) is a balloon borne experiment designed to observe the IGM and CGM through ultraviolet emission. The science instrument on the 1m telescope is a fiber fed integral field unit. 250 independent spectra are taken over the 160 arcmin in diameter field. The instrument exploits current UV technology to create three dimensional views of the gas between galaxies. A successful science flight took place in June of this year. Details of the flight and initial results will be shown.


Vivian U
Institute for Astronomy, University of Hawaii

SED Analysis of Luminous Infrared Galaxies

Luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) are important transition objects between young, blue spirals and old, red ellipticals in the context of galaxy evolution. Their bulk multiwavelength properties are usually exemplified by the spectral energy distribution (SED) of Arp 220, the ``poster child" of ULIRGs. However, there in fact exists a range of spectra shapes for these infrared-luminous objects that cannot be represented by a single template. Here we present comprehensive SEDs for a sample of local (U)LIRGs from the Revised Bright Galaxy Sample (RBGS). Our sample spans the luminosity range $11.1 < \log(L_{\rm IR}/L_{\odot}) < 12.5$. To complement spacecraft (\emph{Chandra, GALEX, HST, Spitzer}) data from the Great Observatories All-sky LIRG Survey (GOALS), we also compiled optical/infrared/submm/radio imaging data from Mauna Kea and from literature to construct full SEDs. We characterized the spectral shapes of these SEDs and analyzed the ratios of the radio, infrared, optical, and x-ray emission as a function of infrared luminosity. Trends observed in various alpha indices will be discussed.


Tatjana Vavilkin
Stony Brook University

Star Formation in Luminous Infrared Galaxies as Traced by GALEX, HST and Spitzer

Luminous Infrared Galaxies (LIRGs) are believed to play an important role in the star formation history of the Universe. Locally, LIRGs are observed to undergo intense bursts of star formation primarily as a result of interaction/merger process. In this talk, I present high-resolution optical Hubble Space Telescope ACS observations of 11 nearby (z $<$ 0.3), cluster-rich LIRGs in the Revised Bright Galaxy Sample (RBGS). The $\sim$ 0.1$^{\prime\prime}$ resolution of this dataset allows for the best possibility thus far to study the properties of star-forming clusters and associations in these luminous IR systems at various interaction stages. Ancillary Spitzer IRAC and GALEX near-UV imaging data are also presented to allow an assessment of the morphology and spatial distribution of star-forming regions at these wavelengths, and to correlate locations of young optical stellar clusters with PAH and UV emission regions. This work is part of the Great Observatories All-sky LIRG Survey (GOALS).


Lisa May Walker
UVa

Mid-Infrared Evidence for Accelerated Evolution in Compact Group Galaxies

We find evidence for accelerated evolution in compact group galaxies from the mid-infrared distribution in colorspace of 42 galaxies from 12 Hickson Compact Groups (HCGs) and the distributions of several comparison samples including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are not uniformly distributed in colorspace, as well as quantitative evidence for a gap. Galaxies in the infall region of the Coma cluster also exhibit a non-uniform distribution and a less well defined gap, which may reflect a similarity with the compact group environment. Neither the Coma Center or interacting samples show evidence of a gap, leading us to speculate that the gap is unique to the environment present in compact groups and cluster outskirts; one of high galaxy density where gas has not been fully processed or stripped.


Steven Warren
University of Minnesota

Connecting Past Star Formation to Current HI Structures

Star formation histories (SFHs) derived from resolved stellar populations have changed the way we can look at galaxies. New techniques that combine the information from SFHs and blue helium burning stars have allowed us to produce spatially resolved ($\sim$8$^{\prime\prime}$) SFH maps. These maps give us the unique opportunity to study past star forming events that may have helped shape the current HI distribution. We combine the SFHs computed from data taken with the Hubble Space Telescope with VLA HI line data (The HI Nearby Galaxy Survey $-$ THINGS) to gain insight into the fundamental processes that create large, HI$-$deficient holes or shells in the interstellar medium. The resolution from the THINGS VLA data ($\sim$7$^{\prime\prime}$) perfectly compliment the SFH maps. Extending the work done by Weisz and collaborators on IC 2574 and Holmberg II, we present preliminary results for two M81 Group dwarf galaxies: M81 dwarf A and Holmberg I. At first glance, the HI distributions of both galaxies appear similar; each contain a ring of high surface brightness gas around a central cavity. Star formation over the past $\sim$500 Myr was at a relatively constant level in both galaxies. However, M81 dwarf A's star formation is centrally concentrated while Holmberg I's permeates through the entire HI disk. We present analysis of the timing, location, and energy associated with SF to explore the connection between stellar feedback and the large HI cavities present in both galaxies. This is a pilot project which will be extended to many more dwarf galaxies with data taken for the NRAO Large Project, VLA-ANGST (P.I. Ott).


Yoshimasa Watanabe
Hokkaido University, Japan

Multi-line molecular gas observations and star formation in the nearby barred spiral galaxy NGC 3627

We present results of $^{13}\rm{CO}(\textit{J}=1-0)$ and $^{12}\rm{CO}(\textit{J}=3-2)$ observation of the nearby barred spiral galaxy NGC 3627 with the Nobeyama 45 m telescope and the Atacama Submillimeter Telescope Experiment (ASTE). We detected $^{13}\rm{CO}(1-0)$ emission in the positions where $^{12}\rm{CO}(1-0)$ emission was detected in the Nobeyama CO Atlas (Kuno et al. 2007). We find that the $^{12}\rm{CO}(1-0)$/$^{13}\rm{CO}(1-0)$ ratios (\textit{R}$_{12/13}$) are higher in a bar (\textit{R}$_{12/13}\sim$25) than in spiral arms and bar ends (\textit{R}$_{12/13}\sim$10-15). Star formation efficiency (SFE) of NGC 3627 derived from H$\alpha$, mid-IR 24 $\mu m$ and $^{12}\rm{CO}(1-0)$ data are $\sim 1.0\times 10^{-9}$~yr$^{-1}$ in the bar, $\sim 2.0\times 10^{-9}$~yr$^{-1}$ in the spiral arms and $\sim 5.0\times 10^{-9}$yr$^{-1}$ in the bar ends, which suggests SFE is low in the bar compared with other regions. But there is little difference between the bar and the spiral arms, if we estimate SFE from the $^{13}\rm{CO}(1-0)$ intensity. We suppose to overestimate a column density of molecular gas due to higher optical depth of the $^{12}\rm{CO}(1-0)$ line than the $^{13}\rm{CO}(1-0)$ line, which leads to the SFE estimated from the $^{12}\rm{CO}(1-0)$ to be lower value. The bar ends, however, remain to have twice higher SFE than the other regions, even though we use $^{13}\rm{CO}(1-0)$ to estimate molecular gas mass. Emission of $^{12}\rm{CO}(3-2)$ line was detected in the center, the bar, the bar end and the spiral arms. In the bar end, peak positions of $^{12}\rm{CO}(3-2)$ / $^{12}\rm{CO}(1-0)$ ratio (\textit{R}$_{3-2/1-0}$), which traces dense molecular gas fraction, are located in the leading side of $^{12}\rm{CO}(1-0)$ intensity peaks which almost coincide with $^{12}\rm{CO}(3-2)$ peaks at the bar end. We interpret the above picture as follows: the molecular gas assembles at the bar end, then streams forward and becomes dense at the leading side of the bar end where SFE is high value.


Lisa Wei
University of Maryland

Gas Mass Fractions and Disk Regrowth Potential in Local Blue-Sequence E/S0s

Recent work has identified a population of local E/S0 galaxies that lie on the blue sequence in color vs. stellar mass parameter space, where spiral galaxies typically reside. While high-mass blue-sequence E/S0s may often be young merger/interaction remnants likely to fade to the red sequence, we focus on blue-sequence E/S0s with lower stellar masses (${M_*} <$ few $\times 10^{10}\,M_{\odot}$), which are characterized by fairly regular morphology and low density field environments where fresh gas infall is possible. This population may provide an evolutionary link between traditional early type galaxies and spirals through disk regrowth. Based on new GBT and VLA data for a representative sample of E/S0s, the atomic gas to stellar mass ratios for most blue-sequence E/S0s range from 0.1 to 1.0, comparable to those of spiral and irregular galaxies. Assuming that the HI is accessible for star formation, we find that at least half of our blue-sequence E/S0s can increase their stellar masses by 10-50\% in 2 Gyr either of two extreme scenarios, exponentially declining star formation (i.e. closed box) or constant star formation (i.e. allowing gas infall). We present evidence that star formation in these galaxies is bursty and likely involves externally triggered gas inflows. We also present CARMA CO 1-0 maps of select blue-sequence E/S0s, discuss these maps' implications for the disk regrowth scenario, and comment on extending this work to higher redshift with ALMA.


Tim Weinzirl
University of Texas at Austin

Constraints on the Assembly and Merger History of Massive Spirals From Their Structural Properties

While major and minor mergers, secular processes, and smooth accretion are known to be relevant galaxy assembly mechanisms, the relative importance and timescales over which they are effective remains debated. We discuss here our results from Weinzirl et al. (2009), where we explore the relative importance of major mergers in the assembly of spiral galaxies and their bulges by comparing our derived structural bulge Sersic index ($n$) and bulge-to-total ratio ($B/T$) of massive galaxies with $\Lambda$CDM-based hierarchical models of galaxy evolution. We perform 2D bulge-disk-bar decomposition on $H$-band images of 143 bright, high stellar mass ($\ge1.0\times10^{10} M_\odot)$ spirals. We find that a large fraction ($\sim69\%$) of bright spirals have $B/T<0.2$, and $\sim76\%$ have low $n<2$ bulges. We compare with predictions from a set of hierarchical models where the merger history and input cold gas physics dictates that a spiral has a present-day low $B/T<0.2$ only if it did not undergo a major merger since $z<2$. As a result, the predicted fraction ($\sim1.6\%$) of high mass spirals, which have undergone a major merger since $z<4$ and host a bulge with a present-day low $B/T<0.2$ is over 30 times smaller than the observed fraction ($\sim66\%$) of high mass spirals with $B/T<0.2$. The results remain similar even in different models where the efficiency of bulge-building during a major merger scales inversely with the cold gas mass fraction. This implies that bulges built via major mergers seriously fail to account for the bulges present in $\sim66\%$ of high mass spirals, and that most of these bulges are likely to have been built by other processes, such as minor mergers, smooth accretion, and secular processes since $z<4$. By revealing the detailed distribution and kinematics of the cold gas component in high redshift galaxies, ALMA will enable us to witness these galaxy assembly mechanisms in action and assess their relative importance.


Mark Westmoquette
University College London

Spatially-resolved studies of super star cluster feedback in starburst galaxies

Understanding starburst-driven outflows is important for many reasons within the context of galaxy evolution. However, to understand outflows on the large scale, the details of feedback mechanisms from individual star clusters must first be understood. In this talk I will discuss recent results from a number of high spatial and spectral resolution optical integral field spectroscopic studies of the ionized gas environment surrounding super star clusters (SSCs) within local-group starbursts (e.g. NGC 1569, M82, NGC 1140). Through dynamical, excitation and density measurements, these studies are allowing us to build up a picture of (1) how power is fed from these clusters into the surrounding ISM: e.g. we find strong evidence for turbulent mixing layers on the surface of ISM gas clumps created by the interaction of the winds and ionizing photons from the nearby star clusters, and (2) what effects the ISM properties have on how this power is directed: e.g. our spatially resolved maps of the ionized nebular properties have allowed us to examine how the environment changes within a starburst and thus explain differences in the evolutionary path of different SSCs. Our work raises many questions regarding the properties of more embedded and/or cooler gas phases that will be addressed with the IFUs coming online on Herschel and JWST, and with ALMA.


Al Wootten
NRAO

ALMA's View of the Redshifted Milky Way

We discuss the energy distribution of the Milky Way at high redshift, using NGC 7331 as a local model, in addition to COBE and other observations. The CO J=3-2, J=4-3 and [C II] lines should be detectable at redshifts near z=3 in 24 hour integrations. Other lines may be detectable for otherr redshifts near z=3 which better position those lines in frequency with respect to the atmosphere and ALMA's receivers.


Lihong Yao
University of Toronto

Evolving Starburst Model of FIR/sub-mm/mm Line Emission and Applications to Nearby Starburst Galaxies

I present a starburst model for FIR/sub-mm/mm line emission of molecular and atomic gas in an evolving starburst region, which is treated as an ensemble of non-interacting hot bubbles which drive spherical shells of swept-up gas into a surrounding uniform gas medium. These bubbles and shells are driven by winds and supernovae within massive star clusters formed during an instantaneous starburst. The underlying stellar radiation from the evolving clusters affects the properties and structure of photodissociation regions in the shells, and hence the spectral energy distributions of the molecular and atomic line emission from these swept-up shells and the associated parent giant molecular clouds contains a signature of the stage evolution of the starburst. By comparing our models with the available observed data of nearby infrared bright galaxies, especially M 82, we constrain the models and in the case of M 82, provide estimates for the age of the recent starburst activity. We also derive the total H$_2$ gas mass in the measured regions of the central 1 kpc starburst disk of M 82. In addition, we apply the model to represent various stages of starburst evolution in a well known sample of nearby luminous infrared galaxies. In this way, we interpret the relationship between the degree of molecular excitation and ratio of FIR to CO luminosity to possibly reflect different stages of the evolution of star-forming activity within their nuclear regions.


B. Ashley Zauderer
University of Maryland

High Resolution Imaging of ULIRGs with CARMA

Ultraluminous Infrared Galaxies (ULIRGs) represent a population that is among the most extreme in our universe, emitting an extraordinary amount of energy at infrared wavelengths from dust heated by either prolific star formation and/or the presence of an active galactic nucleus (AGN). There is also strong evidence that the majority of ULIRGs are interacting galaxies or on-going/recent mergers. There is debate, however, surrounding the intrinsic energy source of many of these highly luminous objects, such as the closest and prototypical ULIRG, Arp 220. We have observed several nearby ULIRGs with CARMA in four configurations, including the longest baseline (up to 2 km) A-array configuration, which has a resolution of $\sim$0.15$^{\prime\prime}$ at 1.3 mm. We have utilized the Paired Antenna Calibration System (PACS) for atmospheric calibration in the longer baseline configurations. In this calibration system, Sunyaev-Zeldovich Array (SZA) antennas were paired with CARMA antennas to allow for a continuous measurement of the atmospheric phase screen on long baselines over time intervals from two seconds to several hours. We performed a variety of tests on bright quasars to confirm the PACS calibration methodology. We present these results along with our scientific results from observations of Arp 220 and other nearby ULIRGs.


Laura Zschaechner
University of New Mexico

Kinematics of The Neutral Halo of NGC 4302

It has recently been realized that kinematic measurements of gaseous halos of nearby galaxies may provide important clues to the origin of such halos and thereby the growth and evolution of galaxy disks. In particular, recent measurements have shown a decrease in rotation speed with height in many halos, leading to various models which attempt to understand this gradient in terms of disk-halo flows and accretion of primordial gas. One observational issue is whether ionized and neutral halos show the same kinematics, suggesting a common origin. The most problematically steep gradient, -30 km/s/kpc, has been found in the ionized halo of the Virgo edge-on NGC 4302 by Heald et al. (2007). Here we present deep VLA HI observations of this galaxy. We clearly detect a vertically extended component. We will present models showing whether the kinematics of this component are best represented by a flare, a warp along the line of sight, or a lagging halo.