Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Astrophysics and Astronomy

PDF

2000

Astronomy Department Faculty Publication Series

Articles 1 - 20 of 20

Full-Text Articles in Physical Sciences and Mathematics

The Two Micron All-Sky Survey: Removing The Infrared Foreground, John E. Gizis, Michael F. Skrutskie Oct 2000

The Two Micron All-Sky Survey: Removing The Infrared Foreground, John E. Gizis, Michael F. Skrutskie

Astronomy Department Faculty Publication Series

We introduce the properties of the Two Micron All-Sky Survey (2MASS) survey for IAU Symposium 204. 2MASS is a near-infrared survey of the entire sky characterized by high reliability and completeness. Catalogs and images for 47% of the sky are now available online. This data release has been used by Wright (2000) and Cambr´esy et al. (2000) to subtract the stellar foreground at 1.25 and 2.2 microns from COBE DIRBE data, revealing the cosmological near-infrared background.

Go to article

Stellar Populations In The Large Magellanic Cloud From 2mass, Sergei Nikolaev, Martin D. Weinberg Mar 2000

Stellar Populations In The Large Magellanic Cloud From 2mass, Sergei Nikolaev, Martin D. Weinberg

Astronomy Department Faculty Publication Series

We present a morphological analysis of the feature-rich 2MASS LMC colormagnitude diagram, identifying Galactic and LMC populations and estimating the density of LMC populations alone. We also present the projected spatial distributions of various stellar populations. The conditions that prevailed when 2MASS observed the LMC provided 10s limiting sensitivity for J <∼ 16.3, H <∼ 15.3, Ks <∼ 14.7. Major populations are identified based on matching morphological features of the color-magnitude diagram with expected positions of known populations, isochrone fits, and analysis of the projected spatial distributions. 2MASS has detected a significant population of asymptotic giant branch (AGB) stars (>∼ 104 sources) and obscured AGB stars ( >∼ 2×103 sources). The LMC populations along the first-ascent red giant branch (RGB) and AGB are quantified. Comparison of the giant luminosity functions in the bar and the outer regions of the LMC shows that both luminosity functions appear consistent with …

Go to article

C32, A Young Star Cluster In Ic 1613, Ted K. Wyder, Paul W. Hodge, Andrew Cole Feb 2000

C32, A Young Star Cluster In Ic 1613, Ted K. Wyder, Paul W. Hodge, Andrew Cole

Astronomy Department Faculty Publication Series

The Local Group irregular galaxy IC 1613 has remained an enigma for many years because of its apparent lack of star clusters. We report the successful search for clusters among several of the candidate objects identified many years ago on photographic plates. We have used a single HST WFPC2 pointing and a series of images obtained with the WIYN telescope under exceptional seeing conditions, examining a total of 23 of the previously published candidates. All but six of these objects were found to be either asterisms or background galaxies. Five of the six remaining candidates possibly are small, sparse clusters …

Go to article

Perturbations Of Spherical Stellar Systems During Flyby Encounters, E Vesperini, Md Weinberg Jan 2000

Perturbations Of Spherical Stellar Systems During Flyby Encounters, E Vesperini, Md Weinberg

Astronomy Department Faculty Publication Series

We study the internal response of a galaxy to an unbound encounter and present a survey of orbital parameters covering typical encounters in different galactic environments. Overall, we conclude that relatively weak encounters by low-mass interloping galaxies can cause observable distortions in the primaries. The resulting asymmetries may persist long after the interloper is evident. We focus our attention on the production of structure in dark halos and in cluster elliptical galaxies. Any distortion produced in a dark halo can distort the embedded stellar disk, possibly leading to the formation of lopsided and warped disks. We show that distant encounters …

Go to article

Discovery Of A Brown Dwarf Companion To Gliese 570abc: A 2mass T Dwarf Significantly Cooler Than Gliese 229b, Adam J. Burgasser, J. Davy Kirkpatrick, Roc M. Cutri, Howard Mccallon, Gene Kopan, John E. Gizis, James Liebert, I. Neill Reid, Michael E. Brown, David G. Monet, Conard C. Dahn, Charles A. Beichman, Michael F. Skrutskie Jan 2000

Discovery Of A Brown Dwarf Companion To Gliese 570abc: A 2mass T Dwarf Significantly Cooler Than Gliese 229b, Adam J. Burgasser, J. Davy Kirkpatrick, Roc M. Cutri, Howard Mccallon, Gene Kopan, John E. Gizis, James Liebert, I. Neill Reid, Michael E. Brown, David G. Monet, Conard C. Dahn, Charles A. Beichman, Michael F. Skrutskie

Astronomy Department Faculty Publication Series

We report the discovery of a widely separated (258.′′3±0.′′4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All Sky Survey (2MASS). Its near-infrared spectrum shows the 1.6 and 2.2 μm CH4 absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (MJ = 16.47±0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L = (2.8±0.3)x10−6 L⊙ and Teff = 750±50 K make it significantly cooler and less …

Go to article

Discovery Of A Bright Field Methane (T-Type) Brown Dwarf By 2mass, Adam J. Burgasser, John C. Wilson, J. Davy Kirkpatrick, Michael F. Skrutskie, Michael R. Colonno, Alan T. Enos, J. D. Smith, Charles P. Henderson, John E. Gizis, Michael E. Brown, James R. Houck Jan 2000

Discovery Of A Bright Field Methane (T-Type) Brown Dwarf By 2mass, Adam J. Burgasser, John C. Wilson, J. Davy Kirkpatrick, Michael F. Skrutskie, Michael R. Colonno, Alan T. Enos, J. D. Smith, Charles P. Henderson, John E. Gizis, Michael E. Brown, James R. Houck

Astronomy Department Faculty Publication Series

We report the discovery of a bright (J = 13.83±0.03) methane brown dwarf, or T dwarf, by the Two Micron All Sky Survey. This object, 2MASSI J0559191-140448, is the first brown dwarf identified by the newly commissioned CorMASS instrument mounted on the Palomar 60-inch Telescope. Near-infrared spectra from 0.9 - 2.35 μm show characteristic CH4 bands at 1.1, 1.3, 1.6, and 2.2 μm, which are significantly shallower than those seen in other T dwarfs discovered to date. Coupled with the detection of an FeH band at 0.9896 and two sets of K I doublets at J-band, we propose that 2MASS …

Go to article

Serendipitous 2mass Discoveries Near The Galactic Plane: A Spiral Galaxy And Two Globular Clusters, Robert L. Hurt, Tom H. Jarrett, J. Davy Kirkpatrick, Roc M. Cutri, Stephen E. Schneider, Mike Skrutskie, Willem Van Driel Jan 2000

Serendipitous 2mass Discoveries Near The Galactic Plane: A Spiral Galaxy And Two Globular Clusters, Robert L. Hurt, Tom H. Jarrett, J. Davy Kirkpatrick, Roc M. Cutri, Stephen E. Schneider, Mike Skrutskie, Willem Van Driel

Astronomy Department Faculty Publication Series

We present the basic properties of three objects near the Galactic Plane—a large galaxy and two candidate globular clusters—discovered in the Two Micron All Sky Survey (2MASS) dataset. All were noted during spot-checks of the data during 2MASS quality assurance reviews. The galaxy is a late-type spiral galaxy (Sc–Sd), ~11 Mpc distant, at l = 236.82°, b = -1.86°. From its observed angular extent of 6.3' in the near infrared, we estimate an extinction-corrected optical diameter of ~9.5', making it larger than most Messier galaxies. The candidate globular clusters are ~2–3’ in extent and are hidden optically behind foreground extinctions …

Go to article

Simulating The Effects Of Intergalactic Gray Dust, Rac Croft, R Dave, L Hernquist, N Katz Jan 2000

Simulating The Effects Of Intergalactic Gray Dust, Rac Croft, R Dave, L Hernquist, N Katz

Astronomy Department Faculty Publication Series

Using a high-resolution cosmological hydrodynamic simulation, we present a method to constrain extinction due to intergalactic gray dust based on the observed magnitudes of distant Type Ia supernovae. We apply several simple prescriptions to relate the intergalactic dust density to the gas density in the simulation, thereby obtaining dust extinctions that may be directly compared with the observed distribution of supernova magnitudes. Our analysis is sensitive to the spatial distribution of gray dust but is not dependent on its intrinsic properties, such as its opacity or grain size. We present an application of our technique to the supernova data of …

Go to article

2mass Extended Sources In The Zone Of Avoidance, T. H. Jarrett, T. Chester, R. Cutri, S. Schneider, J. Rosenberg, J. P. Huchra, J. Mader Jan 2000

2mass Extended Sources In The Zone Of Avoidance, T. H. Jarrett, T. Chester, R. Cutri, S. Schneider, J. Rosenberg, J. P. Huchra, J. Mader

Astronomy Department Faculty Publication Series

No abstract provided.

Go to article

2mass Extended Source Catalog: Overview And Algorithms, T. H. Jarrett, T. Chester, R. Cutri, S. Schneider, M. Skrutskie, J. P. Huchra Jan 2000

2mass Extended Source Catalog: Overview And Algorithms, T. H. Jarrett, T. Chester, R. Cutri, S. Schneider, M. Skrutskie, J. P. Huchra

Astronomy Department Faculty Publication Series

No abstract provided.

Go to article

Embedded Stellar Clusters In The W3/W4/W5 Molecular Cloud Complex, Jm Carpenter, Mh Heyer, Ronald L. Snell Jan 2000

Embedded Stellar Clusters In The W3/W4/W5 Molecular Cloud Complex, Jm Carpenter, Mh Heyer, Ronald L. Snell

Astronomy Department Faculty Publication Series

We analyze the embedded stellar content in the vicinity of the W3/W4/W5 H II regions using the FCRAO Outer Galaxy 12CO (1-0) Survey, the IRAS Point Source Catalog, published radio continuum surveys, and new near-infrared and molecular-line observations. Thirty-four IRAS point sources are identified that have far-infrared colors characteristic of embedded star forming regions, and we have obtained K' mosaics and 13CO (1-0) maps for 32 of them. Ten of the IRAS sources are associated with an OB star and 19 with a stellar cluster, although three OB stars are not identified with a cluster. Half of the …

Go to article

Submillimeter Wave Astronomy Satellite Observations Of Extended Water Emission In Orion, Ronald L. Snell, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick Jan 2000

Submillimeter Wave Astronomy Satellite Observations Of Extended Water Emission In Orion, Ronald L. Snell, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick

Astronomy Department Faculty Publication Series

We have used the Submillimeter Wave Astronomy Satellite to map the ground-state 110 → 101 transition of ortho-H2O at 557 GHz in the Orion molecular cloud. H2O emission was detected in Orion over an angular extent of about 20', or nearly 3 pc. The water emission is relatively weak, with line widths (3-6 km s-1) and VLSR velocities (9-11 km s-1) consistent with an origin in the cold gas of the molecular ridge. We find that the ortho-H2O abundance relative to H2 in the extended gas …

Go to article

Water Abundance In Molecular Cloud Cores, Ronald L. Snell, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick Jan 2000

Water Abundance In Molecular Cloud Cores, Ronald L. Snell, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick

Astronomy Department Faculty Publication Series

We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 110 → 101 transition of ortho-H2O at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, ρ Oph A, NGC 2024, CRL 2591, W3, W3OH, Mon R2, and W33 and was not detected in TMC-1, L134N, and B335. We also present a small map of the H2O emission in S140. Observations of the H218O line were obtained toward S140 and NGC 7538, but no emission was detected. The abundance of ortho-H2O …

Go to article

A Global Photometric Analysis Of 2mass Calibration Data, S Nikolaev, Md Weinberg, Mf Skrutskie, Rm Cutri, Sl Wheelock, Je Gizis, Em Howard Jan 2000

A Global Photometric Analysis Of 2mass Calibration Data, S Nikolaev, Md Weinberg, Mf Skrutskie, Rm Cutri, Sl Wheelock, Je Gizis, Em Howard

Astronomy Department Faculty Publication Series

We present results from the application of a global photometric calibration (GPC) procedure to calibration data from the first 2 years of the Two Micron All Sky Survey (2MASS). The GPC algorithm uses photometry of both primary standards and moderately bright "tracer" stars in 35 2MASS calibration fields. During the first 2 years of the survey, each standard was observed on approximately 50 nights, with about 900 individual measurements. Based on the photometry of primary standard stars and secondary tracer stars and under the assumption that the nightly zero-point drift is linear, the GPC ties together all calibration fields and …

Go to article

Effect Of The Milky Way On Magellanic Cloud Structure, Md Weinberg Jan 2000

Effect Of The Milky Way On Magellanic Cloud Structure, Md Weinberg

Astronomy Department Faculty Publication Series

A combination of analytic models and n-body simulations implies that the structural evolution of the Large Magellanic Cloud (LMC) is dominated by its dynamical interaction with the Milky Way. Although expected at some level, the scope of the involvement has significant observational consequences. First, LMC disk orbits are torqued out of the disk plane, thickening the disk and populating a spheroid. The torque results from direct forcing by the Milky Way tide and, indirectly, from the drag between the LMC disk and its halo resulting from the induced precession of the LMC disk. The latter is a newly reported mechanism …

Go to article

The Distribution Of Water Emission In M17sw, Ronald L. Snell, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick Jan 2000

The Distribution Of Water Emission In M17sw, Ronald L. Snell, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick

Astronomy Department Faculty Publication Series

We present a 17-point map of the M17SW cloud core in the 110 → 101 transition of ortho-H2O at 557 GHz obtained with Submillimeter Wave Astronomy Satellite. Water emission was detected in 11 of the 17 observed positions. The line widths of the H2O emission vary between 4 and 9 km s-1 and are similar to other emission lines that arise in the M17SW core. A direct comparison is made between the spatial extent of the H2O emission and the 13CO J = 5 → 4 emission; the good …

Go to article

Extended [C I] And (Co)-C-13 (5 -> 4) Emission In M17sw, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Dj Hollenbach, Mj Kaufman, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Ronald L. Snell, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick Jan 2000

Extended [C I] And (Co)-C-13 (5 -> 4) Emission In M17sw, Je Howe, Mln Ashby, Ea Bergin, G Chin, Nr Erickson, Pf Goldsmith, M Harwit, Dj Hollenbach, Mj Kaufman, Sc Kleiner, Dg Koch, Da Neufeld, Bm Patten, R Plume, R Schieder, Ronald L. Snell, Jr Stauffer, V Tolls, Z Wang, G Winnewisser, Yf Zhang, Gj Melnick

Astronomy Department Faculty Publication Series

We mapped a 13 × 22 pc region in emission from 492 GHz [C I] and, for the first time, 551 GHz 13CO (5 → 4) in the giant molecular cloud M17SW. The morphologies of the [C I] and 13CO emission are strikingly similar. The extent and intensity of the [C I] and 13CO (5 → 4) emission is explained as arising from photodissociation regions on the surfaces of embedded molecular clumps. Modeling of the 13CO (5 → 4) emission in comparison to 13CO (1 → 0) indicates a temperature gradient across the cloud, peaking …

Go to article

A Spatially Resolved Plerionic X-Ray Nebula Around Psr B0540–69, Ev Gotthelf, Qd Wang Jan 2000

A Spatially Resolved Plerionic X-Ray Nebula Around Psr B0540–69, Ev Gotthelf, Qd Wang

Astronomy Department Faculty Publication Series

We present a high-resolution Chandra X-ray observation of PSR B0540-69, the Crab-like 50 ms pulsar in the Large Magellanic Cloud. We use phase-resolved imaging to decompose the extended X-ray emission, as expected of a synchrotron nebula, from the pointlike emission of the pulsar. The image of the pulsed X-ray emission shows a well-defined point-spread function of the observation, while the resolved nebula has a morphology and size remarkably similar to the Crab nebula, including evidence for a jetlike feature from PSR B0540-69. The patchy outer shell, which most likely represents the expanding blast wave of the supernova, is reminiscent of …

Go to article

The Effects Of Gasdynamics, Cooling, Star Formation, And Numerical Resolution In Simulations Of Cluster Formation, Gf Lewis, A Babul, N Katz, T Quinn, L Hernquist, Dh Weinberg Jan 2000

The Effects Of Gasdynamics, Cooling, Star Formation, And Numerical Resolution In Simulations Of Cluster Formation, Gf Lewis, A Babul, N Katz, T Quinn, L Hernquist, Dh Weinberg

Astronomy Department Faculty Publication Series

We present the analysis of a suite of simulations of a Virgo-mass galaxy cluster. Undertaken within the framework of standard cold dark matter cosmology, these simulations were performed at differing resolutions and with increasingly complex physical processes, with the goal of identifying the effects of each on the evolution of the cluster. We focus on the cluster at the present epoch and examine properties including the radial distributions of density, temperature, entropy, and velocity. We also map "observable" projected properties such as the surface mass density, X-ray surface brightness, and Sunyaev-Zeldovich signature. We identify significant differences between the simulations, which …

Go to article

Title: Recent X-Ray Observations Of Disk Galaxies: Tracing The Dynamic Interstellar Medium, Qd Wang Jan 2000

Title: Recent X-Ray Observations Of Disk Galaxies: Tracing The Dynamic Interstellar Medium, Qd Wang

Astronomy Department Faculty Publication Series

I review recent results from our deep ROSAT and Chandra observations of two galaxies, M101 and NGC 4631, in fields of exceptionally low Galactic extinction. Large amounts of X-ray-emitting gas are detected in these galaxies. Such gas is produced primarily in massive star forming regions and have an average characteristic temperature of a few times $10^6$ K. Cooler gas ($\sim 10^6$ K) is found typically outside galactic disks and may represent outflows from blown-out superbubbles. Propagation of star formation, driven by the expansion of hot gas, appears to be operating in giant HII complexes. A substantial fraction of photo-evaporated gas …

Go to article