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Series

Astrophysics and Astronomy

2008

Astronomy Department Faculty Publication Series

Articles 1 - 30 of 41

Full-Text Articles in Physical Sciences and Mathematics

Globular Cluster Evolution In M87 And Fundamental Plane Ellipticals, Chigurupati Murali, Martin D. Weinberg Feb 2008

Globular Cluster Evolution In M87 And Fundamental Plane Ellipticals, Chigurupati Murali, Martin D. Weinberg

Astronomy Department Faculty Publication Series

The globular cluster population in M87 has decreased measurably through dynamical evolution caused by relaxation, binary heating and time-dependent tidal perturbation. For fundamental plane ellipticals in general, cluster populations evolve more rapidly in smaller galaxies because of the higher mass density. A simple evolutionary model reproduces the observed trend in specific frequency with luminosity for an initially constant relationship. Fits of theoretically evolved populations to M87 cluster data from McLaughlin et al. (1994) show the following: 1) dynamical effects drive evolution in the initial mass and space distributions and can account for the large core in the spatial profile as …

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Evolution Of The Mass Function Of The Galactic Globular Cluster System, E. Vesperini Feb 2008

Evolution Of The Mass Function Of The Galactic Globular Cluster System, E. Vesperini

Astronomy Department Faculty Publication Series

We investigate the evolution of the mass function of the Galactic globular cluster system (GCMF) taking into account the effects of stellar evolution, two-body relaxation, disk shocking and dynamical friction on the evolution of individual globular clusters.We have adopted a log-normal initial GCMF and we have studied in detail the dependence on the initial dispersion and mean value of the GCMF of the fraction of the initial number of clusters surviving after one Hubble time, of the final GCMF, and of the difference between the properties of the GCMF of clusters closer to the Galactic center and of those in …

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Effect Of The Milkyway On Magellanic Cloud Structure, Martin D. Weinberg Feb 2008

Effect Of The Milkyway On Magellanic Cloud Structure, Martin D. 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 …

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The Effect Of The Galactic Spheroid On Globular Cluster Evolution, Chigurupati Murali, Martin D. Weinberg Feb 2008

The Effect Of The Galactic Spheroid On Globular Cluster Evolution, Chigurupati Murali, Martin D. Weinberg

Astronomy Department Faculty Publication Series

We study the combined effects of relaxation, tidal heating and binary heating on globular cluster evolution, exploring the physical consequences of external effects and examining evolutionary trends in the MilkyWay population. Our analysis demonstrates that heating on circular and low-eccentricity orbits can dominate cluster evolution. The results also predict rapid evolution on eccentric orbits either due to strong relaxation caused by the high densities needed for tidal limitation or due to efficient bulge shocking of low density clusters. The combination of effects leads to strong evolution of the population as a whole. For example, within the solar circle, tidally-limited 105M⊙ …

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The 2mass Color-Magnitude Diagram Of The Center Of The Sagittarius Dwarf Galaxy: Photometric Measurements Of A Surprisingly High Mean Metallicity, Andrew A. Cole Feb 2008

The 2mass Color-Magnitude Diagram Of The Center Of The Sagittarius Dwarf Galaxy: Photometric Measurements Of A Surprisingly High Mean Metallicity, Andrew A. Cole

Astronomy Department Faculty Publication Series

We present the Two Micron All Sky Survey (2MASS) (J−K, K) color-magnitude diagram for the region within 1◦ of the center of the Sagittarius dwarf spheroidal galaxy. Using the slope of the red giant branch (RGB), we determine a mean metallicity for the main stellar population of [Fe/H] = −0.5 ±0.2. The Sagittarius RGB possesses a blue tail that overlaps with the foreground Milky Way giant branch, and suggests that ∼ 1/3 of the RGB is more metal-poor than [Fe/H] ~−1. Direct comparison to the Large Magellanic Cloud confirms the metal-rich nature of the bulk of the Sagittarius population. Our …

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Pre-Peak Ram Pressure Stripping In The Virgo Cluster Spiral Galaxy Ngc 4501, B. Vollmer, M. Soida, A. Chung, J. H. Van Gorkom, K. Otmianowska-Mazur, R. Beck, M. Urbanik, J.D. P. Kenney Jan 2008

Pre-Peak Ram Pressure Stripping In The Virgo Cluster Spiral Galaxy Ngc 4501, B. Vollmer, M. Soida, A. Chung, J. H. Van Gorkom, K. Otmianowska-Mazur, R. Beck, M. Urbanik, J.D. P. Kenney

Astronomy Department Faculty Publication Series

VIVA HI observations of the Virgo spiral galaxy NGC 4501 are presented. The HI disk is sharply truncated to the southwest, well within the stellar disk. A region of low surface-density gas, which is more extended than the main HI disk, is discovered northeast of the galaxy center. These data are compared to existing 6 cm polarized radio continuum emission, Hα, and optical broad band images. We observe a coincidence between the western HI and polarized emission edges, on the one hand, and a faint Hα emission ridge, on the other. The polarized emission maxima are located within the gaps …

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Noise-Driven Evolution In Stellar Systems: Theory, Martin D. Weinberg Jan 2008

Noise-Driven Evolution In Stellar Systems: Theory, Martin D. Weinberg

Astronomy Department Faculty Publication Series

We present a theory for describing the evolution of a galaxy caused by stochastic events such as weak mergers, transient spiral structure, orbiting blobs, etc. This noise excites large-scale patterns that drives the evolution of the galactic density profile. In dark-matter haloes, the repeated stochastic perturbations preferentially ring the lowest-order modes of the halo with only a very weak dependence on the details of their source. Shaped by these modes, the profile quickly takes on a nearly self-similar form. We show that this form has the features of the “universal profile” reported by Navarro, Frenk, & White independent of initial …

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Spectra Of Nearby Galaxies Measured With A New Very Broadband Receiver, Gopal Narayanan, Ronald L. Snell, Nr Erickson, Aeree Chung, Mark H. Heyer, Min Yun, William M. Irvine Jan 2008

Spectra Of Nearby Galaxies Measured With A New Very Broadband Receiver, Gopal Narayanan, Ronald L. Snell, Nr Erickson, Aeree Chung, Mark H. Heyer, Min Yun, William M. Irvine

Astronomy Department Faculty Publication Series

Three-millimeter-wavelength spectra of a number of nearby galaxies have been obtained at the Five College Radio Astronomy Observatory (FCRAO) using a new, very broadband receiver. This instrument, which we call the Redshift Search Receiver, has an instantaneous bandwidth of 36 GHz and operates from 74 to 110.5 GHz. The receiver has been built at UMass/FCRAO to be part of the initial instrumentation for the Large Millimeter Telescope (LMT) and is intended primarily for determination of the redshift of distant, dust-obscured galaxies. It is being tested on the FCRAO 14 m by measuring the 3 mm spectra of a number of …

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Aztec Millimetre Survey Of The Cosmos Field: I. Data Reduction And Source Catalogue, K. S. Scott, J. E. Austermann, T. A. Perera, G. W. Wilson, I. Aretxaga, J. J. Bock, D. H. Hughes, Y. Kang, S. Kim, P. D. Mauskopf, D. B. Sanders, N. Scoville, Min Yun Jan 2008

Aztec Millimetre Survey Of The Cosmos Field: I. Data Reduction And Source Catalogue, K. S. Scott, J. E. Austermann, T. A. Perera, G. W. Wilson, I. Aretxaga, J. J. Bock, D. H. Hughes, Y. Kang, S. Kim, P. D. Mauskopf, D. B. Sanders, N. Scoville, Min Yun

Astronomy Department Faculty Publication Series

We present a 1.1 mm wavelength imaging survey covering 0.3 deg2 in the COSMOS field. These data, obtained with the AzTEC continuum camera on the James Clerk Maxwell Telescope, were centred on a prominent large-scale structure overdensity which includes a rich X-ray cluster at z≈ 0.73. A total of 50 mm-galaxy candidates, with a significance ranging from 3.5 to 8.5σ, are extracted from the central 0.15 deg2 area which has a uniform sensitivity of ∼1.3 mJy beam−1. 16 sources are detected with S/N ≥ 4.5, where the expected false-detection rate is zero, of which a …

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Discovery Of A Molecular Outflow In The Haro 6-10 Star-Forming Region, Irena Stojimirović, Gopal Narayanan, Ronald L. Snell Jan 2008

Discovery Of A Molecular Outflow In The Haro 6-10 Star-Forming Region, Irena Stojimirović, Gopal Narayanan, Ronald L. Snell

Astronomy Department Faculty Publication Series

We present high sensitivity 12CO and 13CO J=1!0 molecular line maps covering the full extent of the parsec scale Haro 6-10 Herbig-Haro (HH) flow. We report the discovery of a molecular CO outflow along the axis of parsec-scale HH flow. Previous molecular studies missed the identification of the outflow probably due to their smaller mapping area and the confusing spectral features present towards the object. Our detailed molecular line study of the full 1.6 pc extent of the optical flow shows evidence for both blueshifted and redshifted gas set in motion by Haro 6-10 activity. The molecular outflow is centered …

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Time-Dependent Secular Evolution In Galaxies, Martin D. Weinberg Jan 2008

Time-Dependent Secular Evolution In Galaxies, Martin D. Weinberg

Astronomy Department Faculty Publication Series

Lynden-Bell & Kalnajs (1972) presented a useful formula for computing the long-range torque between spiral arms and the disk at large. The derivation uses second-order perturbation theory and assumes that the perturbation slowly grows over a very long time: the time-asymptotic limit. This formula has been widely used to predict the angular momentum transport between spiral arms and stellar bars between disks and dark-matter halos. However, this paper shows that the LBK time-asymptotic limit is not appropriate because the characteristic evolution time for galaxies is too close to the relevant dynamical times. We demonstrate that transients, not present in the …

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The Relations Among 8, 24 And 160 Mu M Dust Emission Within Nearby Spiral Galaxies, Gj Bendo, Bt Draine, Cw Engelbracht, G Helou, Md Thornley, C Bot, Ba Buckalew, D Calzetti, Da Dale, J Hollenbach, A Li, J Moustakas Jan 2008

The Relations Among 8, 24 And 160 Mu M Dust Emission Within Nearby Spiral Galaxies, Gj Bendo, Bt Draine, Cw Engelbracht, G Helou, Md Thornley, C Bot, Ba Buckalew, D Calzetti, Da Dale, J Hollenbach, A Li, J Moustakas

Astronomy Department Faculty Publication Series

We investigate the relations among the stellar continuum-subtracted 8 μm polycyclic aromatic hydrocarbon (PAH 8 μ m) emission, 24 μm hot dust emission and 160 μm cold dust emission in 15 nearby face-on spiral galaxies in the Spitzer Infrared Nearby Galaxies Survey sample. The relation between PAH 8 and 24 μm emission measured in ∼2 kpc regions is found to exhibit a significant amount of scatter, and strong spatial variations are observed in the (PAH 8 μ m)/24 μm surface brightness ratio. In particular, the (PAH 8 μ m)/24 μm surface brightness ratio is observed to be high in the …

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Spitzer Irac Infrared Colours Of Submillimetre-Bright Galaxies, Min Yun, I Aretxaga, Mln Ashby, J Austermann, Gg Fazio, M Giavalisco, Js Huang, Dh Hughes, S Kim, Jd Lowenthal, T Perera, K Scott, G Wilson, Jd Younger Jan 2008

Spitzer Irac Infrared Colours Of Submillimetre-Bright Galaxies, Min Yun, I Aretxaga, Mln Ashby, J Austermann, Gg Fazio, M Giavalisco, Js Huang, Dh Hughes, S Kim, Jd Lowenthal, T Perera, K Scott, G Wilson, Jd Younger

Astronomy Department Faculty Publication Series

High-redshift submillimetre-bright galaxies identified by blank field surveys at millimetre and submillimetre wavelengths appear in the region of the Infra Red Array Camera (IRAC) colour–colour diagrams previously identified as the domain of luminous active galactic nuclei (AGNs). Our analysis using a set of empirical and theoretical dusty starburst spectral energy distribution (SED) models shows that power-law continuum sources associated with hot dust heated by young (≲100 Myr old), extreme starbursts at z > 2 also occupy the same general area as AGNs in the IRAC colour–colour plots. A detailed comparison of the IRAC colours and SEDs demonstrates that the two populations …

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The Great Observatories Origins Deep Survey - Vlt/Fors2 Spectroscopy In The Goods-South Field: Part Iii, E Vanzella, S Cristiani, M Dickinson, M Giavalisco, H Kuntschner, J Haase, M Nonino, P Rosati, C Cesarsky, Hc Ferguson, Rae Fosbury, A Grazian, La Moustakas, A Rettura, P Popesso, A Renzini, D Stern Jan 2008

The Great Observatories Origins Deep Survey - Vlt/Fors2 Spectroscopy In The Goods-South Field: Part Iii, E Vanzella, S Cristiani, M Dickinson, M Giavalisco, H Kuntschner, J Haase, M Nonino, P Rosati, C Cesarsky, Hc Ferguson, Rae Fosbury, A Grazian, La Moustakas, A Rettura, P Popesso, A Renzini, D Stern

Astronomy Department Faculty Publication Series

No abstract provided.

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Baryon Dynamics, Dark Matter Substructure, And Galaxies, Dh Weinberg, S Colombi, R Dave, N Katz Jan 2008

Baryon Dynamics, Dark Matter Substructure, And Galaxies, Dh Weinberg, S Colombi, R Dave, N Katz

Astronomy Department Faculty Publication Series

By comparing a collisionless cosmological N-body simulation (DM) to a smoothed particle hydrodynamics simulation (SPH) with the same initial conditions, we investigate the correspondence between dark matter subhalos produced by collisionless dynamics and galaxies produced by dissipative gas dynamics in a dark matter background. When galaxies in the SPH simulation fall into larger groups and become satellites, they retain local dark matter concentrations (SPH subhalos) whose mass is typically 5 times the galaxy baryonic mass (compared to the simulation's universal ratio Ωdm/Ωb 7.5). The more massive subhalos of the SPH simulation generally have corresponding subhalos of …

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An Aztec 1.1 Mm Survey Of The Goods-N Field - I. Maps, Catalogue And Source Statistics, Ta Perera, El Chapin, Je Austermann, Ks Scott, Gw Wilson, M Halpern, A Pope, D Scott, Min Yun, Jd Lowenthal, G Morrison, I Aretxaga, Jj Bock, K Coppin, M Crowe, L Frey, Dh Hughes, Y Kang, S Kim, Pd Mauskopf Jan 2008

An Aztec 1.1 Mm Survey Of The Goods-N Field - I. Maps, Catalogue And Source Statistics, Ta Perera, El Chapin, Je Austermann, Ks Scott, Gw Wilson, M Halpern, A Pope, D Scott, Min Yun, Jd Lowenthal, G Morrison, I Aretxaga, Jj Bock, K Coppin, M Crowe, L Frey, Dh Hughes, Y Kang, S Kim, Pd Mauskopf

Astronomy Department Faculty Publication Series

We have conducted a deep and uniform 1.1 mm survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field with AzTEC on the James Clerk Maxwell Telescope. Here, we present the first results from this survey including maps, the source catalogue and 1.1 mm number counts. The results presented here were obtained from a 245 arcmin2 region with a near uniform coverage to a depth of 0.96–1.16 mJy beam−1. Our robust catalogue contains 28 source candidates detected with S/N ≥ 3.75, only ∼1– 2 of which are expected to be spurious detections. Of these source candidates, eight …

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The Physical Scale Of The Far-Infrared Emission In The Most Luminous Submillimeter Galaxies, Jd Younger, Gg Fazio, Dj Wilner, Mln Ashby, R Blundell, Ma Gurwell, Js Huang, D Iono, Ab Peck, Gr Petitpas, Ks Scott, Gw Wilson, Min Yun Jan 2008

The Physical Scale Of The Far-Infrared Emission In The Most Luminous Submillimeter Galaxies, Jd Younger, Gg Fazio, Dj Wilner, Mln Ashby, R Blundell, Ma Gurwell, Js Huang, D Iono, Ab Peck, Gr Petitpas, Ks Scott, Gw Wilson, Min Yun

Astronomy Department Faculty Publication Series

We present high-resolution submillimeter interferometric imaging of two of the brightest high-redshift submillimeter galaxies known: GN 20 and AzTEC1 at 0.8'' and 0.3'' resolution, respectively. Our data—the highest resolution submillimeter imaging of high-redshift sources accomplished to date—were collected in three different array configurations: compact, extended, and very extended. We derive angular sizes of 0.6'' and 1.0'' for GN 20 and 0.3'' and 0.4'' for AzTEC1 from modeling their visibility functions as a Gaussian and an elliptical disk, respectively. Because both sources are B-band dropouts, they likely lie within a relatively narrow redshift window around z ~ 4, which indicates …

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A Bright, Dust-Obscured, Millimetre-Selected Galaxy Beyond The Bullet Cluster (1e0657-56), Gw Wilson, Dh Hughes, I Aretxaga, H Ezawa, Je Austermann, S Doyle, D Ferrusca, I Hernandez-Curiel, R Kawabe, T Kitayama, K Kohno, A Kuboi, H Matsuo, Pd Mauskopf, Y Murakoshi, A Montana, P Natarajan, T Oshima, N Ota, Ta Perera, J Rand, Ks Scott, K Tanaka, M Tsuboi, Cc Williams, N Yamaguchi, Min Yun Jan 2008

A Bright, Dust-Obscured, Millimetre-Selected Galaxy Beyond The Bullet Cluster (1e0657-56), Gw Wilson, Dh Hughes, I Aretxaga, H Ezawa, Je Austermann, S Doyle, D Ferrusca, I Hernandez-Curiel, R Kawabe, T Kitayama, K Kohno, A Kuboi, H Matsuo, Pd Mauskopf, Y Murakoshi, A Montana, P Natarajan, T Oshima, N Ota, Ta Perera, J Rand, Ks Scott, K Tanaka, M Tsuboi, Cc Williams, N Yamaguchi, Min Yun

Astronomy Department Faculty Publication Series

Deep 1.1 mm continuum observations of 1E0657−56 (the ‘Bullet Cluster’) taken with the millimeter-wavelength camera AzTEC on the 10-m Atacama Submillimeter Telescope Experiment (ASTE), have revealed an extremely bright (S1.1 mm= 15.9 mJy) unresolved source. This source, MMJ065837−5557.0, lies close to a maximum in the density of underlying mass distribution, towards the larger of the two interacting clusters as traced by the weak-lensing analysis of Clowe et al. Using optical–infrared (IR) colours, we argue that MMJ065837−5557.0 lies at a redshift of z= 2.7 ± 0.2. A lensing-derived mass model for the Bullet Cluster shows a critical …

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Measuring Star Formation In Local And Distant Galaxies, D Calzetti Jan 2008

Measuring Star Formation In Local And Distant Galaxies, D Calzetti

Astronomy Department Faculty Publication Series

I review measurements of star formation in nearby galaxies in the UV-to-FIR wavelength range, and discuss their impact on SFR determinations in intermediate and high redshift galaxy populations. Existing and upcoming facilities will enable precise cross-calibrations among the various indicators, thus bringing them onto a common scale.

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Limits On Hot Galactic Halo Gas From X-Ray Absorption Lines, Y Yao, Ma Nowak, Qd Wang, Ns Schulz, Cr Canizares Jan 2008

Limits On Hot Galactic Halo Gas From X-Ray Absorption Lines, Y Yao, Ma Nowak, Qd Wang, Ns Schulz, Cr Canizares

Astronomy Department Faculty Publication Series

Although the existence of large-scale hot gaseous halos around massive disk galaxies has been theorized for a long time, there is yet very little observational evidence. We report the Chandra and XMM-Newton grating spectral detection of O VII and Ne IX Kα absorption lines along the sight line of 4U 1957+11. The line absorption is consistent with the interstellar medium in origin. Attributing these line absorptions to the hot gas associated with the Galactic disk, we search for the gaseous halo around the Milky Way by comparing this sight line with more distant ones (toward the X-ray binary LMC X-3 …

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Chandra Observation Of The Edge-On Spiral Ngc 5775: Probing The Hot Galactic Disc/Halo Connection, Jt Li, Z Li, Qd Wang, Ja Irwin, J Rossa Jan 2008

Chandra Observation Of The Edge-On Spiral Ngc 5775: Probing The Hot Galactic Disc/Halo Connection, Jt Li, Z Li, Qd Wang, Ja Irwin, J Rossa

Astronomy Department Faculty Publication Series

We study the edge-on galaxy NGC 5775, utilizing a 58.2 ks Chandra ACIS-S observation together with complementary Hubble Space Telescope (HST) ACS, Spitzer IRAC and other multi-wavelength data sets. This edge-on galaxy, with its disc-wide active star formation, is particularly well suited for studying the disc/halo interaction on subgalactic scales. We detect 27 discrete X-ray sources within the D25 region of the galaxy, including an ultra-luminous source with a 0.3–7 keV luminosity of ∼7 × 1040 erg s−1. The source-removed diffuse X-ray emission shows several prominent extraplanar features, including a ∼10 kpc diameter ‘shell-like’ …

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Swas Observations Of Water In Molecular Outflows, J Franklin, Ronald L. Snell, Mj Kaufman, Gj Melnick, Da Neufeld, Dj Hollenbach, Ea Bergin Jan 2008

Swas Observations Of Water In Molecular Outflows, J Franklin, Ronald L. Snell, Mj Kaufman, Gj Melnick, Da Neufeld, Dj Hollenbach, Ea Bergin

Astronomy Department Faculty Publication Series

We present detections of the ground-state 110→ 101 transition of ortho-H2O at 557 GHz in 18 molecular outflows based on data from the Submillimeter Wave Astronomy Satellite (SWAS). These results are combined with ground-based observations of the J = 1–0 transitions of 12CO and 13CO obtained at the Five College Radio Astronomy Observatory (FCRAO). Data from Infrared Space Observatory (ISO) for a subset of the outflows are also discussed. Assuming that the SWAS water-line emission originates from the same gas traced by CO emission, we find that the outflowing …

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Self-Regulated Fueling Of Galaxy Centers: Evidence For Star Formation Feedback, E Schinnerer, T Boker, Ds Meier, D Calzetti Jan 2008

Self-Regulated Fueling Of Galaxy Centers: Evidence For Star Formation Feedback, E Schinnerer, T Boker, Ds Meier, D Calzetti

Astronomy Department Faculty Publication Series

Using new, high-resolution interferometric observations of the CO and HCN molecules, we directly compare the molecular and ionized components of the interstellar medium in the center of the nearby spiral galaxy IC 342, on spatial scales of 10 pc. The morphology of the tracers suggests that the molecular gas flow caused by a large-scale stellar bar has been strongly affected by the mechanical feedback from recent star formation activity within the central 100 pc in the nucleus of the galaxy. Possibly, stellar winds and/or supernova shocks originating in the nuclear star cluster have compressed, and likely pushed outward, the infalling …

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The Five College Radio Astronomy Observatory Co Mapping Survey Of The Taurus Molecular Cloud, Gopal Narayanan, Mh Heyer, C Brunt, Pf Goldsmith, Ronald L. Snell, D Li Jan 2008

The Five College Radio Astronomy Observatory Co Mapping Survey Of The Taurus Molecular Cloud, Gopal Narayanan, Mh Heyer, C Brunt, Pf Goldsmith, Ronald L. Snell, D Li

Astronomy Department Faculty Publication Series

The FCRAO Survey of the Taurus molecular cloud observed the 12CO and 13CO J = 1–0 emission from 98 deg2 of this important, nearby, star-forming region. This set of data with 45'' resolution comprises the highest spatial dynamic range image of an individual molecular cloud constructed to date and provides valuable insights to the molecular gas distribution, kinematics, and the star formation process. In this contribution, we describe the observations, calibration, data processing, and characteristics of the noise and line emission of the survey. The angular distribution of 12CO and 13CO emission over 1 km …

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Large-Scale Structure Of The Molecular Gas In Taurus Revealed By High Linear Dynamic Range Spectral Line Mapping, Pf Goldsmith, M Heyer, Gopal Narayanan, Ronald L. Snell, D Li, C Brunt Jan 2008

Large-Scale Structure Of The Molecular Gas In Taurus Revealed By High Linear Dynamic Range Spectral Line Mapping, Pf Goldsmith, M Heyer, Gopal Narayanan, Ronald L. Snell, D Li, C Brunt

Astronomy Department Faculty Publication Series

We report the results of a 100 deg2 survey of the Taurus molecular cloud region in 12CO and 13CO J = 1→ 0. The image of the cloud in each velocity channel includes 3 × 106 Nyquist-sampled pixels on a 20'' grid. The high sensitivity and large spatial dynamic range of the maps reveal a very complex, highly structured cloud morphology, including filaments, cavities, and rings. The axes of the striations seen in the 12CO emission from relatively diffuse gas are aligned with the direction of the magnetic field. We have developed a statistical …

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Star Formation Rate Determinations, Daniela Calzetti Jan 2008

Star Formation Rate Determinations, Daniela Calzetti

Astronomy Department Faculty Publication Series

I review determinations of star formation rates (SFR) from the ultraviolet to the infrared, in the context of their use for galaxies and galaxy surveys. The mid-infrared SFR indicators have garnered interest in recent years thanks to the Spitzer capabilities and the opportunities offered by the upcoming Herschel Space Telescope. I discuss what we have learned in the mid-infrared from studies of local galaxies combining Spitzer with HST and other data.

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Spitzer Observations Of Star Formation In The Extreme Outer Disk Of M83 (Ngc5236), H Dong, D Calzetti, M Regan, D Thilker, L Bianchi, Gr Meurer, F Walter Jan 2008

Spitzer Observations Of Star Formation In The Extreme Outer Disk Of M83 (Ngc5236), H Dong, D Calzetti, M Regan, D Thilker, L Bianchi, Gr Meurer, F Walter

Astronomy Department Faculty Publication Series

Spitzer Infrared Array Camera (IRAC) observations of two fields in the extended UV disk (XUV-disk) of M83 have been recently obtained, ~3 R HII away from the center of the galaxy (R HII = 6.6 kpc). Galaxy Evolution Explorer (GALEX) UV images have shown the two fields to host in situ recent star formation. The IRAC images are used in conjunction with GALEX data and new H I imaging from The H I Nearby Galaxy Survey (THINGS) to constrain stellar masses and ages of the UV clumps in the fields, and to relate the local recent star formation to the …

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Star Formation Rates In Lyman Break Galaxies: Radio Stacking Of Lbgs In The Cosmos Field And The Sub-Mu Jy Radio Source Population, Cl Carilli, N Lee, P Capak, E Schinnerer, Ks Lee, H Mccraken, Min Yun, N Scoville, V Smolcic, M Giavalisco, A Datta, Y Taniguchi, Cm Urry Jan 2008

Star Formation Rates In Lyman Break Galaxies: Radio Stacking Of Lbgs In The Cosmos Field And The Sub-Mu Jy Radio Source Population, Cl Carilli, N Lee, P Capak, E Schinnerer, Ks Lee, H Mccraken, Min Yun, N Scoville, V Smolcic, M Giavalisco, A Datta, Y Taniguchi, Cm Urry

Astronomy Department Faculty Publication Series

We present an analysis of the radio properties of large samples of Lyman break galaxies (LBGs) at z ~ 3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z ~ 3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90 ± 0.21 μJy. The stacked emission is unresolved, with a size <1, or a physical size <8 kpc. The total star formation rate implied by this radio luminosity is 31 ± 7 M yr−1, based on the radio-FIR correlation in low-redshift star-forming galaxies. The star formation rate derived from a similar analysis of the UV luminosities is 17 M yr−1, without any correction for …

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Spectroscopic Confirmation Of An Extreme Starburst At Redshift 4.547, P Capak, Cl Carilli, N Lee, T Aldcroft, H Aussel, E Schinnerer, Gw Wilson, Min Yun, A Blain, M Giavalisco, O Ilbert, J Kartaltepe, Ks Lee, H Mccracken, B Mobasher, M Salvato, S Sasaki, Ks Scott, K Sheth, Y Shioya, D Thompson, M Elvis, Db Sanders, Nz Scoville, Y Tanaguchi Jan 2008

Spectroscopic Confirmation Of An Extreme Starburst At Redshift 4.547, P Capak, Cl Carilli, N Lee, T Aldcroft, H Aussel, E Schinnerer, Gw Wilson, Min Yun, A Blain, M Giavalisco, O Ilbert, J Kartaltepe, Ks Lee, H Mccracken, B Mobasher, M Salvato, S Sasaki, Ks Scott, K Sheth, Y Shioya, D Thompson, M Elvis, Db Sanders, Nz Scoville, Y Tanaguchi

Astronomy Department Faculty Publication Series

We report the spectroscopic confirmation of a submillimeter galaxy (SMG) at z = 4.547 with an estimated LIR = (0.5-2.0) × 1013 L. The spectra, mid-IR, and X-ray properties indicate the bolometric luminosity is dominated by star formation at a rate of >1000 M yr−1. Multiple, spatially separated components are visible in the Lyα line with an observed velocity difference of up to 380 km s−1 and the object morphology indicates a merger. The best-fit spectral energy distribution and spectral line indicators suggest the object is 2-8 Myr old and contains >1010 M …

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Ongoing Assembly Of Massive Galaxies By Major Merging In Large Groups And Clusters From The Sdss, Dh Mcintosh, Yc Guo, J Hertzberg, N Katz, Hj Mo, Fc Van Den Bosch, Xh Yang Jan 2008

Ongoing Assembly Of Massive Galaxies By Major Merging In Large Groups And Clusters From The Sdss, Dh Mcintosh, Yc Guo, J Hertzberg, N Katz, Hj Mo, Fc Van Den Bosch, Xh Yang

Astronomy Department Faculty Publication Series

We investigate the incidence of major mergers creating massive (Mstar > 1011 M⊙) galaxies in present-day (z≤ 0.12) groups and clusters. Using a volume-limited sample of 845 groups with dark matter halo masses above 2.5 × 1013 M⊙, we isolate 221 galaxy pairs with ≤1.5 r-band magnitude differences, ≤30 kpc projected separations and combined masses above 1011 M⊙. We fit the r-band images of each pair as the line-of-sight projection of symmetric models and identify 38 mergers by the presence of residual asymmetric structure associated with …

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