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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Early-type Unit Type:Legacy Astronomical Image |
Description:VLA atomic hydrogen of the central dominant galaxy of the Fornax Cluster, Fornax A (a.k.a. NGC 1316). The gas is shown as blue contours on an optical image from the Digital Sky Survey. The main body of the Fornax A is typical of early type galaxies, but at fainter light levels the galaxy exhibits a peculiar morphology, with many shells, ripples and loops. The VLA spectral line observations show gas associated with the galaxy NGC 1317 just to the north, the barred galaxy NGC 1310 to the west, and in several small clounds around the main body of NGC 1316. Its possible that the gas clouds are left over from a merger event which fueled the central radio source.
Radio data are VLA DnC-array observations at 54"x43" resolution. HI contours start at a level of 2x10<sup>19</sup> atoms cm<sup>-2</sup>, with successive contours a factor of two higher. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Peculiar Unit Type:Legacy Astronomical Image |
Description:A composite image of the optical light (green), star forming regions (yellow and pink), and cold atomic hydrogen gas (blue) in the well known merger remnant NGC 7252, the "Atoms for Peace" galaxy. The nickname of this object derives from its optical appearance, specifically the pair of tidal tails (reminiscent of a peace sign) and the loops of material surrounding the optical body (reminiscent of early depictions of an atom). This system is the result of two spiral galaxies which collided and merged into a single object. The atomic hydrogen observations, taken with the VLA in its C- and D-array configurations, show the tidal tails to be rich in gas, confirming the gas-rich nature of the progenitor disks. They also show the inner regions to be relatively free of cold atomic gas. These observations support the idea that two gas-rich disk galaxies can merge together to form a circular gas-poor object similar to an early-type galaxy.
VLA C+D array observations with a resolution of 27"x16". Optical image is B-band image taken by P. Guhathakurta with the CTIO 4m telescope. The continuum subtracted Halpha image was taken using the KPNO 2.1m telescope. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Peculiar Unit Type:Legacy Astronomical Image |
Description:Composite image of the nearby merging galaxy, NGC 4038/9, also known as "The Antennae", due to the antennae-like morphology of its two prominant tidal tails. The image shows a true-color representation of the optical starlight, with the neutral atomic gas depicted in blue. This system is composed of two spiral galaxies which are in the process of slamming together, throwing off two long, narrow tidal streamers. The atomic hydrogen observations, obtained with the VLA, provide information on both the distribution of the gas (as shown), as well as its kinematics. The latter are useful for constraining numerical models of the encounter to help astronomers construct its past and future evolution.
Optical image obtained with the CTIO 0.9m telescope, and is a combination of CCD exposures taken in the Blue, Visible, and Red part of the spectrum. The VLA observations are a combination of C-array and D-array observations. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Peculiar Unit Type:Legacy Astronomical Image |
Description:A composite image of the optical light (green and yellow), star forming regions (pinkish white), and cold atomic hydrogen gas (blue) in the classic bridge-tail system Arp 295. The atomic hydrogen observations, taken with the VLA in its C and D-array configurations, discovered 9 previously unknown group members (eight of which are seen in this image; the ninth lies outside the display area). Some of these are labelled in an alternative version of this image.
VLA C+D array observations, with a resolution of 28". Optical image and Continuum subtracted Halpha image, showing warm gas ionized by young, hot stars, were obtained with the KPNO 0.9m telescope in 10/92. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Peculiar Unit Type:Legacy Astronomical Image |
Description:A composite image of the optical light (green), warm gas (yellow and pink), and cold atomic hydrogen gas (blue) in the well known merger remnant NGC 3921, also known as Arp 224. NGC 3921 is the galaxy to the lower left of the image. It is in a small group with three other nearby galaxies (2 of which are labeled in this alternative version of these same data): the spiral galaxy NGC3916 (upper right), the dwarf galaxy known as MCG +09-19-213 (far right), and a small unnamed disk galaxy just to the right of NGC 3921. NGC 3921 is the result of two spiral galaxies which collided and merged into a single object. The atomic hydrogen observations, taken with the VLA in its C- and D-array configurations, show the narrow tail that extends directly south from the galaxy's main body is gas rich, while the tidal loop/plume that emerges from the lower right of the galaxy, loops around, and then extends to the upper left is gas poor, suggesting that this system is the result of the collision between a gas-rich and a gas-poor disk galaxy. The inner regions are relatively free of cold atomic gas, supporting the idea that two disk galaxies can merge together to form a circular gas-poor object similar to an early-type galaxy.
VLA C+D array observations with a resolution of 20". Optical image is an R-band image, and both this image and the continuum subtracted Halpha image were obtained with the KPNO 2.1m telescope. The velocity of MCG +09-19-213 fell to one edge of the bandpass, so its HI has not been completely mapped. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Peculiar Unit Type:Legacy Astronomical Image |
Description:A composite image of the optical light (green), warm gas (yellow), and cold atomic hydrogen gas (blue) in the merging system NGC 520, also known as Arp 157. NGC 520 is the galaxy near the middle, and is believed to be the result of two disk galaxies currently colliding; a galactic "train wreck". It has a nearby dwarf companion named UGC 957 (labeled in this image). The atomic hydrogen observations, taken with the VLA in its C- and D-array configurations, reveals a nearly complete gaseous ring going right through UGC 957, and astronomers are not sure how this came to be.
VLA C+D array observations with a resolution of 24". Optical image is an R-band image, and both this image and the continuum subtracted Halpha image were obtained with the KPNO 0.9m telescope. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Early-type Unit Type:Legacy Astronomical Image |
Description:VLA atomic hydrogen observations of the NGC 5018 group. The upper panel is the optical image from the Digital Sky Survey, while the lower panel shows the same optical image to fainter light levels, with contours indicating the distribution of the cold atomic gas. NGC 5018 is classified as a normal E3 elliptical galaxy, but at fainter light levels the galaxy exhibits a peculiar morphology, with many shells, ripples and loops. The VLA spectral line observations shows gas associated with a number of spiral galaxies in the group, and a few clouds which are not apparently associated with any optically identified system. Most interestingly, there is an extended gas "bridge" of material connecting two spirals on either side of NGC 5018, and the gaseous bridge appears to bend to avoid the elliptical.
Radio data are VLA D-array observations at 60" resolution. HI contours start at a level of 3x10<sup>19</sup> atoms cm<sup>-2</sup>, with successive contours a factor of two higher. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Peculiar Unit Type:Legacy Astronomical Image |
Description:A composite image of the optical light (green and yellow) and cold atomic hydrogen gas (blue) in the "Ring Galaxy" Arp 143 (a.k.a. NGC 2444/5). The atomic hydrogen observations, taken with the VLA in its C and D-array configurations, shows a suprising gaseous tidal tails reaching far to the north of this galaxy, to a total distance of 175 kpc or 570,000 light years in length (for Ho=75 km/s/Mpc). There was no hint of this tidal tail in previous optical images. Deeper optical imaging may show a hint of starlight associated with the tail, but it is mostly a gaseous structure. Notice gas also associated with the classical grand-design spiral galaxy to the right
VLA C+D array observations obtained by Appleton et al. (1987), with a resolution of 28". Optical image is R-band image taken by J. Hibbard with the KPNO 0.9m telescope in 10/92. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Early-type Unit Type:Legacy Astronomical Image |
Description:VLA atomic hydrogen observations of the shell galaxy NGC 2865. The gas is shown as yellow contours on an optical image from the Digital Sky Survey. The main body of the NGC 2865 is typical of early type galaxies, but at fainter light levels the galaxy exhibits a peculiar morphology, with many shells, ripples and loops. The VLA spectral line observations shows gas within the main body of the elliptical, but also distributed in an extended ring around it.
Radio data are VLA B and C-array observations at 20" resolution. HI contours start at a level of 3x10<sup>19</sup> atoms cm<sup>-2</sup>, with successive contours a factor of two higher. [show more]
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Creator:Legacy Astronomical Images Series:Galaxies Series Unit:Spiral Unit Type:Legacy Astronomical Image |
Description:The galaxy M81 is a spiral galaxy about 11 million light-years from Earth. It is about 50,000 light-years across. In the optical (not shown), the galaxy is known as a "Grand Design" spiral, for its pair of symmetric, well-defined spiral arms. This image, which only shows the cold atomic hydrogen gas in the galaxy, clearly shows that the gas also follows this grand design pattern. In this pseudocolor image, red indicates higher gas densities and blue weaker emission.
The observations consist of data taken with the VLA in the B-array, C-array and D-array configurations for a total of more than 60 hours of observing time. Two pointings and two velocity settings were used. The resolution is 12". The continuum sources have not been removed from the map. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Stars Unit Type:Legacy Astronomical Image |
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Stars Unit Type:Legacy Astronomical Image |
Description:Supergiant stars such as Betelgeuse have very extended atmospheres, the properties of which are poorly understood.
We observed Betelgeuse for 11 hours on 21 December 1996 with the Very Large Array (VLA) in its highest-resolution (A) configuration. At a wavelength of 7 mm, the angular resolution achieved (40 mas) is sufficient to have resolved Betelgeuse's atmostphere. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Stars Unit Type:Legacy Astronomical Image |
Description:A radio image of IM Pegasi superimposed upon an artist's depiction of the star system. IM Pegasi is a binary star system located about 300 light years from Earth in the constellation Pegasus. The system consists of a red giant star about 13 times the size of the Sun, and a much smaller yellow dwarf star comparable in both size and color to the Sun. The red giant star is several thousand times more active than the Sun and thus has large dark star spots which cover a significant portion of its surface. The two stars of the binary orbit each other about their mutual center of mass. The orbital path of the primary is indicated by the dark grey line and that of the secondary by the light grey line. The radio image, outlined by the faded blue contour lines, traces charged particles accelerated in energetic, magnetic events near opposite sides of the visible surface of the giant star. The precise alignment of the radio image with respect to the giant star is conjectural. IM Pegasi is the guide star for the NASA/Stanford Gravity Probe B mission.
The contours (and light green hue) represent an 8.4GHz (3.6cm) phase-referenced VLBI image of IM Pegasi (HR8703), the guide star for the NASA/Stanford Gravity Probe B mission. The image was produced from data acquired over a 16 hour period on 18/19 September 1999. The observations were made using a global array of radio telescopes including the ten VLBA antennas, the phased VLA, the 100-m Effelsberg antenna, and the three 70-m NASA/JPL DSN antennas. The resolution of the VLBI array is approximately 0.6 mas in the horizontal, i.e., east-west, direction. The separation of the peaks of the radio lobes is approximately 1.5 mas. The contours displayed in the radio image are drawn at 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of the peak brightness of 13.0 mJy/beam. The dynamic range of the image is 170:1. IM Pegasi is an RS CVn binary system consisting of a giant primary and dwarf secondary. An artist's depiction of the binary system is included in the background of the radio image. The illustrated orbits of the primary star (spotted and red) and secondary star (yellow), indicated by the dark grey and light grey lines, respectively, are approximations to the actual orbits. The sizes of the primary and secondary stars are each inferred from optical spectroscopic and photometric observations (Berdyugina et al. 1999; Lebach et al. 1999). The precise alignment of the radio image with respect to the primary star is conjectural. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Star Forming Regions Unit Type:Legacy Astronomical Image |
Description:The 6 cm radiograph shows the bipolar HII region S106 (SH 2-106) which is illuminated by a recently formed BO star. The star is still partially buried in its placental molecular cloud as shown by 2.6 mm carbon monoxide observations. Three noteworthy features of the radio image: (1) The exciting star is visible as a point radio source since it has a powerful, ionized stellar wind. (2) The star is located in the middle of a radio shadow, a 3" x 20" region free from ionized gas. This feature of the map indicates the presence of a disc or ring of circumstellar material located in the line of sight which blocks all ionizing ultraviolet photons in its equatorial plane. Gas lying in the shadow of this ring cannot be ionized by stellar UV photons, hence it does not emit radio waves. Since UV photons scattered from the HII region also do not appear capable of ionizing this region, we conclude that the "radio-shadow" must be occupied by dense neutral gas with n > 10^5 cm^ -3. Supporting evidence for a large scale neutral disc seen edgeon surrounding the exciting star can be found in high resolution mm-wave maps of the distribution of molecular gas and in formaldehyde (H2CO) absorption maps made at the VLA. The inner edge of the disc lies within 0.1" (~7 x 10^14 cm < 30 A.U.) of the star since the strong ionization front expected at the inner edge is hidden within the stellar wind at lambda=6cm. (3) The structure of the large scale HII region shows numerous clumps and filaments and a systematic supersonic expansion of the plasma away from the exciting star. The kinematics and morphology of the nebula suggest that the dynamics of the gas are dominated by the powerful wind blowing from the central star.
Observing runs - 1981 February 8 and December 12 at the VLA in A- and C-configurations, using 27 antennas. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Star Forming Regions Unit Type:Legacy Astronomical Image |
Description:This panorama of a section of the Milky Way in the constellations of Scutum and Aquila illustrates the dynamic interplay between the birth and death of massive stars in our Galaxy. The image is a composite of a radio image constructed from observations taken in several configurations of the Very Large Array at a wavelength of 20 cm for the MAGPIS survey with mid-infrared data taken as part of the GLIMPSE survey conducted by the Spitzer Space Telescope. The radio data are coded red, the long-wavelength infrared data (at 8 micrometers) green, and the shorter wavelength infrared data blue-white; yellow regions in the image show places where both radio and infrared emission is prominent. Normal stars are brightest at the shortest wavelengths, showing up as the myriad of blue-white points. Birthsites of the youngest massive stars show as yellow clumps -- radiation from the newborn stars heats surrounding dust producing infrared emission, while the ultraviolet light from these stars separates electrons from hydrogen atoms giving rise to radio emission. More mature stars have managed to destroy the dust nearby leaving red cores surrounded by yellow, then green, shells as the temperature drops far from the stars. The prominent red arcs mark the sites where massive stars have died in titanic explosions and blasted their gas light years into space at thousands of miles per second; their radio emission is produced as electrons, accelerated to nearly the speed of light by the outward moving blast waves, spiral in the Galactic magnetic field. The diffuse green glow reveals the tiny dust particles that suffuse interstellar space along the band of the Milky Way; dark filaments superposed on this emission show regions where the gas and dust are so thick that no light can get through -- regions in which future generations of stars will form.
20cm observations were taken in the B, C and D configurations of the VLA using a hexagonal pointing grid that covers the Galactic plane +- 0.8 degrees in this region. Observations of each field were taken at multiple hour angles to help reduce sidelobes. Typical total integration times are about one hour per field. The data are mapped using 2 arcsec pixels. Very large-scale structures were added from single-dish data using the AIPS IMERG task. For more details on the radio observations and reduction, see Helfand et al. (2006) "MAGPIS: A Multi-Array Galactic Plane Imaging Survey", AJ, 131, 2525. The infrared data come from the Spitzer GLIMPSE survey. The 3.6, 4.5 and 8.0 micron bands are assigned approximately to blue, blue-green, and green, with the 20cm radio assigned to red. The colors were assigned using the Lupton et al. (2004, PASP, 116, 133) algorithm, which preserves colors even for saturated sources. The colors are consistent for objects with the same optical-to-radio flux ratios and so they can be compared directly in different regions. Green regions are dominated by 8 micron dust emission, red regions are non-thermal radio emission, and yellow regions have both dust and radio emission. Note the frequent occurrence of red radio cores with thin yellow shells and surrounding green dust emission. Supernova remnants show up as bright red because their associated IR emission is much fainter. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Star Forming Regions Unit Type:Legacy Astronomical Image |
Description:This panorama of a section of the Milky Way in the constellations of Scutum and Aquila illustrates the dynamic interplay between the birth and death of massive stars in our Galaxy. The image is a composite of a radio image constructed from observations taken in several configurations of the Very Large Array at a wavelength of 20 cm for the MAGPIS survey with mid-infrared data taken as part of the GLIMPSE survey conducted by the Spitzer Space Telescope. The radio data are coded red, the long-wavelength infrared data (at 8 micrometers) green, and the shorter wavelength infrared data blue-white; yellow regions in the image show places where both radio and infrared emission is prominent. Normal stars are brightest at the shortest wavelengths, showing up as the myriad of blue-white points. Birthsites of the youngest massive stars show as yellow clumps -- radiation from the newborn stars heats surrounding dust producing infrared emission, while the ultraviolet light from these stars separates electrons from hydrogen atoms giving rise to radio emission. More mature stars have managed to destroy the dust nearby leaving red cores surrounded by yellow, then green, shells as the temperature drops far from the stars. The prominent red arcs mark the sites where massive stars have died in titanic explosions and blasted their gas light years into space at thousands of miles per second; their radio emission is produced as electrons, accelerated to nearly the speed of light by the outward moving blast waves, spiral in the Galactic magnetic field. The diffuse green glow reveals the tiny dust particles that suffuse interstellar space along the band of the Milky Way; dark filaments superposed on this emission show regions where the gas and dust are so thick that no light can get through -- regions in which future generations of stars will form.
20cm observations were taken in the B, C and D configurations of the VLA using a hexagonal pointing grid that covers the Galactic plane +- 0.8 degrees in this region. Observations of each field were taken at multiple hour angles to help reduce sidelobes. Typical total integration times are about one hour per field. The data are mapped using 2 arcsec pixels. Very large-scale structures were added from single-dish data using the AIPS IMERG task. For more details on the radio observations and reduction, see Helfand et al. (2006) "MAGPIS: A Multi-Array Galactic Plane Imaging Survey", AJ, 131, 2525. The infrared data come from the Spitzer GLIMPSE survey. The 3.6, 4.5 and 8.0 micron bands are assigned approximately to blue, blue-green, and green, with the 20cm radio assigned to red. The colors were assigned using the Lupton et al. (2004, PASP, 116, 133) algorithm, which preserves colors even for saturated sources. The colors are consistent for objects with the same optical-to-radio flux ratios and so they can be compared directly in different regions. Green regions are dominated by 8 micron dust emission, red regions are non-thermal radio emission, and yellow regions have both dust and radio emission. Note the frequent occurrence of red radio cores with thin yellow shells and surrounding green dust emission. Supernova remnants show up as bright red because their associated IR emission is much fainter. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Star Forming Regions Unit Type:Legacy Astronomical Image |
Description:This panorama of a section of the Milky Way in the constellations of Scutum and Aquila illustrates the dynamic interplay between the birth and death of massive stars in our Galaxy. The image is a composite of a radio image constructed from observations taken in several configurations of the Very Large Array at a wavelength of 20 cm for the MAGPIS survey with mid-infrared data taken as part of the GLIMPSE survey conducted by the Spitzer Space Telescope. The radio data are coded red, the long-wavelength infrared data (at 8 micrometers) green, and the shorter wavelength infrared data blue-white; yellow regions in the image show places where both radio and infrared emission is prominent. Normal stars are brightest at the shortest wavelengths, showing up as the myriad of blue-white points. Birthsites of the youngest massive stars show as yellow clumps -- radiation from the newborn stars heats surrounding dust producing infrared emission, while the ultraviolet light from these stars separates electrons from hydrogen atoms giving rise to radio emission. More mature stars have managed to destroy the dust nearby leaving red cores surrounded by yellow, then green, shells as the temperature drops far from the stars. The prominent red arcs mark the sites where massive stars have died in titanic explosions and blasted their gas light years into space at thousands of miles per second; their radio emission is produced as electrons, accelerated to nearly the speed of light by the outward moving blast waves, spiral in the Galactic magnetic field. The diffuse green glow reveals the tiny dust particles that suffuse interstellar space along the band of the Milky Way; dark filaments superposed on this emission show regions where the gas and dust are so thick that no light can get through -- regions in which future generations of stars will form.
20cm observations were taken in the B, C and D configurations of the VLA using a hexagonal pointing grid that covers the Galactic plane +- 0.8 degrees in this region. Observations of each field were taken at multiple hour angles to help reduce sidelobes. Typical total integration times are about one hour per field. The data are mapped using 2 arcsec pixels. Very large-scale structures were added from single-dish data using the AIPS IMERG task. For more details on the radio observations and reduction, see Helfand et al. (2006) "MAGPIS: A Multi-Array Galactic Plane Imaging Survey", AJ, 131, 2525. The infrared data come from the Spitzer GLIMPSE survey. The 3.6, 4.5 and 8.0 micron bands are assigned approximately to blue, blue-green, and green, with the 20cm radio assigned to red. The colors were assigned using the Lupton et al. (2004, PASP, 116, 133) algorithm, which preserves colors even for saturated sources. The colors are consistent for objects with the same optical-to-radio flux ratios and so they can be compared directly in different regions. Green regions are dominated by 8 micron dust emission, red regions are non-thermal radio emission, and yellow regions have both dust and radio emission. Note the frequent occurrence of red radio cores with thin yellow shells and surrounding green dust emission. Supernova remnants show up as bright red because their associated IR emission is much fainter. [show more]
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Creator:Legacy Astronomical Images Series:Active Galactic Nuclei Series Unit:Quasars Unit Type:Legacy Astronomical Image |
Description:These images of 0735+178, obtained by Gomez, Agudo, Marscher, Alberdi & Gabuzda, provide the highest resolution observations of this source to date, revealing a twisted jet in the inner regions of 0735+178. Two sharp projected bends of 90 deg. can be observed within 2 mas (1 mas=3.3 pc at the distance of 0735+178, z=0.424) from the core. The magnetic field appears to smoothly follow one of the bends in the jet, suggesting that this structure may be the result of a precessing nozzle in the jet of 0735+178. In order to test this hypothesis we have performed 3D hydrodynamic relativistic simulations of a precessing jet, using the numerical code developed by Aloy, Marti, & Iba±ez. The images to the left show the time evolution (from top to bottom) of the expected emission from a precessing jet, when viewed at 10 deg. A twisted jet structure, similar to that observed in 0735+178, can easily be distinguished. Further VLBA observations should provide the necessary information to test whether the fluid in the jet of 0735+178 moves ballistically away from the core, or in such a way that the fluid velocity vectors remain parallel to the jet axis. This will provide information regarding the hydrodynamic properties of the jet in 0735+178, as well as the ambient medium through which it propagates.
Left panel: 22 GHz; right panel: 43 GHz [show more]
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Creator:Legacy Astronomical Images Series:Active Galactic Nuclei Series Unit:Seyferts Unit Type:Legacy Astronomical Image |
Description:An optical image in H-alpha light of the central part of NGC 4258, which shows jet-like structures emerging from the core on a scale of a kiloparsec (3260 light-years). The inset shows the newly discovered molecular disk that contains water vapor masers. Their velocities are color coded (blue for approaching, red for receding and green for stationary with respect to the galaxy) and define nearly perfect Keplerian motion around an unseen object of 40 million solar masses. [show more]
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Creator:Legacy Astronomical Images Series:Active Galactic Nuclei Series Unit:Quasars Unit Type:Legacy Astronomical Image |
Description:VLA image of the famous "blowtorch" jet in the galaxy NGC6251.
The data was obtained from the VLA archive for analysis with X-ray images from the Chandra X-ray Observatory and XMM-Newton.
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Supernova Remnants Unit Type:Legacy Astronomical Image |
Description:Cassiopeia A is the remnant of a supernova explosion that occured over 300 years ago in our Galaxy, at a distance of about 11,000 light years from us. Its name is derived from the constellation in which it is seen: Cassiopeia, the Queen. A supernova is the explosion that occurs at the end of a massive star's life; and Cassiopeia A is the expanding shell of material that remains from such an explosion. This radio image of Cassiopeia A was created with the National Science Foundation's Very Large Array telescope in New Mexico. This image was made at 3 different frequencies: 1.4 GHz (L band), 5.0 GHz (C band), and 8.4 GHz (X band). Cassiopeia A is one of the brightest radio sources in the sky, and has been a popular target of study for radio astronomers for decades. The material that was ejected from the supernova explosion can be seen in this image as bright filaments. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Supernova Remnants Unit Type:Legacy Astronomical Image |
Description:Cassiopeia A (Cas A) is the remnant of the supernova event which was quite possibly witnessed by Flamsteed in AD 1680. At that time the outer layers of a massive star were ejected with high velocity, sweeping up a shell of the surrounding interstellar material. This shell has now decelerated sufficiently so that the more slowly expanding material from deeper within the star is breaking through the shell from inside. The passage of this ejecta through the shell gives rise to conical extensions which leave crater-like structures in their wake.
Bandwidth synthesis used to improve spatial frequency content Details: Fully processed radiograph of the total intensity of CasA, deconvolved from the 4096 x 4096 pixel "dirty" image and beam via a Maximum Entropy Method ('VM') algorithm in 20 minutes of CPU time on a Cray X-MP. [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Supernova Remnants Unit Type:Legacy Astronomical Image |
Description:A radio image of Cassiopeia A, which is a young supernova remnant nearby in our Galaxy, composited with a photograph of the NRAO Very Large Array telescope at dusk. Cassiopeia A is the brightest radio source in the sky except the Sun. It is about 10 light years across and about 10,000 light years away. It is the remnant of a supernova explosion that occurred approximately 300 years ago.
The VLA image of Cassiopeia A is courtesy of NRAO and R. Perley, and was made at a frequency of 1.38 GHz using the NRAO Very Large Array. The resolution is 1.3". The brightness scale runs from deep brown through blue to white. In addition, areas where the brightness gradients are steep are highlighted faintly in red. The original radio data was taken from the NRAO CD-ROM: "Images of the Radio Universe", 1992. [show more]
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Creator:Legacy Astronomical Images Series:Miscellaneous Series Unit:Cosmology Unit Type:Legacy Astronomical Image |
Description:These radio maps, obtained with the VLA, show 21 gravitational lenses discovered as part of CLASS (Cosmic Lens All-Sky Survey) plus a rediscovery of a previously known lens system. A gravitational lens is formed when a galaxy lies close to the line of sight to a more distant object - in these cases, a radio-loud quasar. The action of the galaxy's gravitational field bends the light from the distant object, forming multiple images of it. To find the systems pictured here, 16503 radio sources were examined with the VLA. Followup observations using radio (MERLIN and VLBA) telescopes and the Hubble Space Telescope in the optical were then used to confirm the systems as gravitational lenses. Systems normally have two images (e.g. 0218+357) or four images (e.g. 0712+472 where two images are blended and the fourth image is not quite visible in this discovery image). A few more exotic cases are also detected (e.g. six images in 1359+154). Each image is 3.2 arcseconds on a side, except for 2108+213 which is twice as big.
These images are the 22 gravitational lenses found from 30-second A-configuration snapshots at 8.4 GHz of 16503 flat-spectrum radio sources. The intrinsically simple, quasi-pointlike structure of such sources allows easy detection of multiple-image gravitational lensing and also allows it to be distinguished from intrinsic structure such as small jets by subsequent observations at higher resolution. These images have a resolution of 220mas and were used to search for lens systems in the splitting range 0.3-15 arcseconds. (Bandwidth smearing prevents reliable searches beyond about 20-30 arcsec). [show more]
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Creator:Legacy Astronomical Images Series:Galactic Sources Series Unit:Star Forming Regions Unit Type:Legacy Astronomical Image |
Description:Combining VLA 8 GHz continuum emission data from the archive, taken over the past ~15 years by different observing groups, we have found the G19.61-0.23 region to contain more than 9 ultra-compact H-II regions of gas ionized by massive young stars. This image clearly shows that high-mass stars form in clusters.
The white contour indicate the 10-sigma level of the image noise level. [show more]
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