Physical Sciences and Mathematics Commons^™

Hsc-Clauds Survey: The Star Formation Rate Functions Since Z  ∼  2 And Comparison With Hydrodynamical Simulations, V. Picouet, S. Arnouts, E. Le Floc'h, T. Mountard, K. Kraljic, O. Illbert, M. Sawicki, G. Desprez, C. Laigle, D. Schiminovich, S. De La Torre, S. Gwyn, H. J. Mccracken, Y. Dobois, R. Davé, S. Toft, J. R. Weaver, M. Shuntov, O. B. Kauffmann

Astronomy Department Faculty Publication Series

Context. Star formation rate functions (SFRFs) give an instantaneous view of the distribution of star formation rates (SFRs) in galaxies at different epochs. They are a complementary and more stringent test for models than the galaxy stellar mass function, which gives an integrated view of the past star formation activity. However, the exploration of SFRFs has been limited thus far due to difficulties in assessing the SFR from observed quantities and probing the SFRF over a wide range of SFRs.

Aims. We overcome these limitations thanks to an original method that predicts the infrared luminosity from the rest-frame UV/optical color …

A Z=1.82 Analog Of Local Ultra-Massive Elliptical Galaxies, M Onodera, E Daddi, R Gobat, M Cappellari, N Arimoto, A Renzini, Y Yamada, Hj Mccracken, C Mancini, P Capak, M Carollo, A Cimatti, M Giavalisco, O Ilbert, X Kong, S Lilly, K Motohara, K Ohta, Db Sanders, N Scoville, N Tamura, Y Taniguchi

Astronomy Department Faculty Publication Series

We present observations of a very massive galaxy at z = 1.82 that show that its morphology, size, velocity dispersion, and stellar population properties are fully consistent with those expected for passively evolving progenitors of today's giant ellipticals. These findings are based on a deep optical rest-frame spectrum obtained with the Multi-Object InfraRed Camera and Spectrograph on the Subaru Telescope of a high-z passive galaxy candidate (pBzK) from the COSMOS field, for which we accurately measure its redshift of z = 1.8230 and obtain an upper limit on its velocity dispersion σ⋆ < 326  km s−1. By detailed stellar population modeling of both the galaxy broadband spectral energy distribution and the rest-frame optical spectrum, we derive a star formation-weighted age and formation redshift of tsf ≃ 1–2 Gyr and z …

The Nature Of Submillimetre Galaxies In Cosmological Hydrodynamic Simulations, R Dave, K Finlator, Bd Oppenheimer, M Fardal, N Katz, D Keres, Dh Weinberg

Astronomy Department Faculty Publication Series

We study the nature of rapidly star-forming galaxies at z= 2 in cosmological hydrodynamic simulations, and compare their properties to observations of submillimetre galaxies (SMGs). We identify simulated SMGs as the most rapidly star-forming systems that match the observed number density of SMGs. In our models, SMGs are massive galaxies sitting at the centres of large potential wells, being fed by smooth infall and gas-rich satellites at rates comparable to their star formation rates (SFRs). They are not typically undergoing major mergers that significantly boost their quiescent SFR, but they still often show complex gas morphologies and kinematics. Our …

Mid-Infrared Spectroscopy Of Candidate Active Galactic Nuclei-Dominated Submillimeter Galaxies, K Coppin, A Pope, K Menendez-Delmestre, Dm Alexander, Js Dunlop, E Egami, J Gabor, E Ibar, Rj Ivison, Je Austermann, Aw Blain, Sc Chapman, Dl Clements, L Dunne, S Dye, D Farrah, Dh Hughes, Amj Mortier, Mj Page, M Rowan-Robinson, D Scott, C Simpson, I Smail, Am Swinbank, M Vaccari, Min Yun

Astronomy Department Faculty Publication Series

Spitzer spectroscopy has revealed that 80% of submm galaxies (SMGs) are starburst (SB)-dominated in the mid-infrared. Here we focus on the remaining 20% that show signs of harboring powerful active galactic nuclei (AGNs). We have obtained Spitzer-InfraRed Spectrograph spectroscopy of a sample of eight SMGs that are candidates for harboring powerful AGNs on the basis of IRAC color selection (S _{8 μm}/S _{4.5 μm}>2, i.e., likely power-law mid-infrared spectral energy distributions). SMGs with an AGN dominating (50%) their mid-infrared emission could represent the "missing link" sources in an evolutionary sequence involving a major merger. First …

Deep 1.1 Mm-Wavelength Imaging Of The Goods-S Field By Aztec/Aste - I. Source Catalogue And Number Counts, Ks Scott, Min Yun, Gw Wilson, Je Austermann, E Aguilar, I Aretxaga, H Ezawa, D Ferrusca, B Hatsukade, Dh Hughes, D Iono, M Giavalisco, R Kawabe, K Kohno, Pd Mauskopf, T Oshima, Ta Perera, J Rand, Y Tamura, T Tosaki, M Velazquez, Cc Williams, M Zeballos

Astronomy Department Faculty Publication Series

We present the first results from a confusion-limited map of the Great Observatories Origins Deep Survey-South (GOODS-S) taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment. We imaged a field to a 1σ depth of 0.48–0.73 mJy beam⁻¹, making this one of the deepest blank-field surveys at mm-wavelengths ever achieved. Although by traditional standards our GOODS-S map is extremely confused due to a sea of faint underlying sources, we demonstrate through simulations that our source identification and number counts analyses are robust, and the techniques discussed in this paper are relevant for other deeply confused surveys. …

Evidence Of A Fast Evolution Of The Uv Luminosity Function Beyond Redshift 6 From A Deep Hawk-I Survey Of The Goods-S Field, M Castellano, A Fontana, K Boutsia, A Grazian, L Pentericci, R Bouwens, M Dickinson, M Giavalisco, P Santini, S Cristiani, Et. Al.

Astronomy Department Faculty Publication Series

No abstract provided.

The Unusual N Iv]-Emitter Galaxy Gds J033218.92-275302.7: Star Formation Or Agn-Driven Winds From A Massive Galaxy At Z=5.56, E Vanzella, A Grazian, M Hayes, L Pentericci, D Schaerer, M Dickinson, S Cristiani, M Giavalisco, A Verhamme, M Nonino, P Rosati

Astronomy Department Faculty Publication Series

Aims. We investigate the nature of the source GDS J033218.92-275302.7 at redshift 5.56.
Methods. The spectral energy distribution of the source is well-sampled by 16 bands photometry from UV-optical (HST and VLT), near infrared, near infrared (VLT) to mid-infrared (Spitzer). The detection of a signal in the mid-infrared Spitzer/IRAC bands 5.8, 8.0 - where the nebular emission contribution is less effective - suggests that there is a Balmer break, the signature of an underlying stellar population formed at earlier epochs. The high-quality VLT/FORS2 spectrum shows a clear Ly emission line, together with semi-forbidden N IV] 1483.3-1486.5 also …

Aztec Half Square Degree Survey Of The Shades Fields - I. Maps, Catalogues And Source Counts, Je Austermann, Min Yun, Et. Al.

Astronomy Department Faculty Publication Series

We present the first results from the largest deep extragalactic mm-wavelength survey undertaken to date. These results are derived from maps covering over 0.7 deg², made at λ= 1.1 mm, using the AzTEC continuum camera mounted on the James Clerk Maxwell Telescope. The maps were made in the two fields originally targeted at λ= 850 μm with the Submillimetre Common-User Bolometer Array (SCUBA) in the SCUBA Half-Degree Extragalactic Survey (SHADES) project, namely the Lockman Hole East (mapped to a depth of 0.9–1.3 mJy rms) and the Subaru/XMM–Newton Deep Field (mapped to a depth of 1.0–1.7 mJy rms). …

Star Formation And Mass Assembly In High Redshift Galaxies, P. Santini, A. Fontana, A. Grazian, S. Salimbeni, F. Fiore, F. Fontanot, K. Boutsia, M. Castellano, S. Cristiani, C. De Santis, S. Gallozzi, E. Giallongo, N. Menci, M. Nonino, D. Paris, L. Pentericci, E. Vanzella

Astronomy Department Faculty Publication Series

Aims. The goal of this work is to infer the star formation properties and the mass assembly process of high redshift (0.3 ≤ z < 2.5) galaxies from their IR emission using the 24 μm band of MIPS-Spitzer. Methods. We used an updated version of the GOODS-MUSIC catalog, which has multiwavelength coverage from 0.3 to 24 μm and either spectroscopic or accurate photometric redshifts.We describe how the catalog has been extended by the addition of mid-IR fluxes derived from theMIPS 24 μm image.We compared two different estimators of the star formation rate (SFR hereafter). One is the total infrared emission derived from 24 μm, estimated using both synthetic and empirical IR templates. The other one is a multiwavelength fit to the full galaxy SED, which automatically accounts for dust reddening and age–star formation activity degeneracies. For both estimates, we computed the SFR density and the specific SFR. Results. We show that the two SFR indicators are roughly consistent, once the uncertainties involved are taken into account. However, they show a systematic trend, IR-based estimates exceeding the fit-based ones as the star formation rate increases. With this new catalog, we show that: a) at z > 0.3, the star formation rate is correlated well with stellar mass, and this relationship seems to steepen with redshift if one relies on IR–based estimates of the SFR; b) the contribution to the global SFRD by massive galaxies increases with redshift up to ≃ 2.5, more rapidly than for galaxies of lower mass, but appears to flatten at higher z; c) despite this increase, the most important contributors to the SFRD at any z are galaxies …

Structural Properties Of Central Galaxies In Groups And Clusters, Yc Guo, Dh Mcintosh, Hj Mo, N Katz, Fc Van Den Bosch, M Weinberg, Sm Weinmann, A Pasquali, Xh Yang

Astronomy Department Faculty Publication Series

Using a statistically representative sample of 911 central galaxies (CENs) from the Sloan Digital Sky Survey (SDSS) Data Release 4 group catalogue, we study how the structure (shape and size) of the first rank (by stellar mass) group and cluster members depends on (1) galaxy stellar mass (Mstar), (2) the global environment defined by the dark matter halo mass (Mhalo) of the host group and (3) the local environment defined by their special halocentric position. We quantify the structure of SDSS galaxies with a galfit-based pipeline that fits two-dimensional Sérsic models to the r-band image data. Through tests with simulated …

Dust-Corrected Star Formation Rates Of Galaxies. I. Combinations Of H Alpha And Infrared Tracers, Rc Kennicutt, Cn Hao, D Calzetti, J Moustakas, Da Dale, G Bendo, Cw Engelbracht, Bd Johnson, Jc Lee

Astronomy Department Faculty Publication Series

We combine Hα emission-line and infrared (IR) continuum measurements of two samples of nearby galaxies to derive dust attenuation-corrected star formation rates (SFRs). We use a simple energy balance based method that has been applied previously to H II regions in the Spitzer Infrared Nearby Galaxies Survey, and extend the methodology to integrated measurements of galaxies. We find that our composite Hα + IR based SFRs are in excellent agreement with attenuation-corrected SFRs derived from integrated spectrophotometry, over the full range of SFRs (0.01-80 M sun yr-1) and attenuations (0-2.5 mag) studied. We find that the combination of Hα and …

Hubble Space Telescope/Advanced Camera For Surveys Morphology Of Ly Alpha Emitters At Redshift 5.7 In The Cosmos Field, Y Taniguchi, Et. Al.

Astronomy Department Faculty Publication Series

We present detailed morphological properties of Lyα emitters (LAEs) at z ≈ 5.7 in the COSMOS field based on Hubble Space Telescope Advanced Camera for Surveys (ACS) data. The ACS imaging in the F814W filter covered 85 LAEs of the 119 LAEs identified in the full two square degree field, and 47 LAEs of them are detected in the ACS images. Nearly half of them are spatially extended with a size larger than 0.15 arcsec (∼0.88 kpc at z = 5.7) and up to 0.4 arcsec (∼2.5 kpc at z = 5.7). The others are nearly unresolved compact objects. Two …

Expanding The Search For Galaxies At Z Similar To 7-10 With New Nicmos Parallel Fields, Alaina L. Henry, Brian Siana, Matthew A. Malkan, Matthew L.N. Ashby, Carrie R. Bridge, Ranga-Ram Chary, James W. Colbert, Mauro Giavalisco, Harry I. Teplitz, Patrick J. Mccarthy

Astronomy Department Faculty Publication Series

We have carried out a search for galaxies at z ∼ 7–10 in ∼14.4 arcmin2 of new NICMOS parallel imaging taken in the Great Observatories Origins Deep Survey (5.9 arcmin2), the Cosmic Origins Survey (7.2 arcmin2), and SSA22 (1.3 arcmin2). These images reach 5σ sensitivities of J110 = 26.0–27.5 (AB), and combined they increase the amount of deep near-infrared data by more than 60% in fields where the investment in deep optical data has already been made. We find no z > 7 candidates in our survey area, consistent with the Bouwens et al. measurements at z ∼ 7 and …

Biases And Uncertainties In Physical Parameter Estimates Of Lyman Break Galaxies From Broadband Photometry, Sk Lee, R Idzi, Hc Ferguson, Rs Somerville, T Wiklind, M Giavalisco

Astronomy Department Faculty Publication Series

We investigate the biases and uncertainties in estimates of physical parameters of high-redshift Lyman break galaxies (LBGs), such as stellar mass, mean stellar population age, and star formation rate (SFR), obtained from broadband photometry. These biases arise from the simplifying assumptions often used in fitting the spectral energy distributions (SEDs). By combining ΛCDM hierarchical structure formation theory, semianalytic treatments of baryonic physics, and stellar population synthesis models, we construct model galaxy catalogs from which we select LBGs at redshifts z ∼ 3.4, 4.0, and 5.0. The broadband photometric SEDs of these model LBGs are then analyzed by fitting galaxy template …

The Aztec/Sma Interferometric Imaging Survey Of Submillimeter-Selected High-Redshift Galaxies, Jd Younger, Gg Fazio, Js Huang, Min Yun, Gw Wilson, Mln Ashby, Ma Gurwell, Ab Peck, Gr Petitpas, Dj Wilner, Dh Hughes, I Aretxaga, S Kim, Ks Scott, J Austermann, T Perera, Jd Lowenthal

Astronomy Department Faculty Publication Series

We present results from a continuing interferometric survey of high-redshift submillimeter galaxies (SMGs) with the Submillimeter Array, including high-resolution (beam size ~2 arcsec) imaging of eight additional AzTEC 1.1 mm selected sources in the COSMOS field, for which we obtain six reliable (peak signal-to-noise ratio (S/N) >5 or peak S/N >4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N >4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric follow up. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology—including …

The Dynamics Of Satellite Disruption In Cold Dark Matter Haloes, Jh Choi, Md Weinberg, N Katz

Astronomy Department Faculty Publication Series

We investigate the physical mechanisms of tidal heating and satellite disruption in cold dark matter host haloes using N-body simulations based on cosmological initial conditions. We show the importance of resonant shocks and resonant torques with the host halo to satellite heating. A resonant shock (torque) couples the radial (tangential) motion of a satellite in its orbit to its phase space. For a satellite on a circular orbit, an inner Lindblad resonance (ILR)-like resonance dominates the heating and this heating results in continuous satellite mass loss. We estimate the requirements for simulations to achieve these dynamics using perturbation theory. Both …

Comparison Of H Alpha And Uv Star Formation Rates In The Local Volume: Systematic Discrepancies For Dwarf Galaxies, Jc Lee, Ag De Paz, C Tremonti, Rc Kennicutt, S Salim, M Bothwell, D Calzetti, J Dalcanton, D Dale, C Engelbracht, Sjjg Funes, B Johnson, S Sakai, E Skillman, L Van Zee, F Walter, D Weisz

Astronomy Department Faculty Publication Series

Using a complete sample of ~300 star-forming galaxies within 11 Mpc of the Milky Way, we evaluate the consistency between star formation rates (SFRs) inferred from the far ultraviolet (FUV) non-ionizing continuum and Hα nebular emission, assuming standard conversion recipes in which the SFR scales linearly with luminosity at a given wavelength. Our analysis probes SFRs over 5 orders of magnitude, down to ultra-low activities on the order of ~10-4 M sun yr-1. The data are drawn from the 11 Mpc Hα and Ultraviolet Galaxy Survey (11HUGS), which has obtained Hα fluxes from ground-based narrowband imaging, and UV fluxes from …

The Chandra Cosmos Survey. I. Overview And Point Source Catalog, M Elvis, F Civano, C Vignali, S Puccetti, F Fiore, N Cappelluti, Tl Aldcroft, A Fruscione, G Zamorani, A Comastri, M Brusa, R Gilli, T Miyaji, F Damiani, Am Koekemoer, A Finoguenov, H Brunner, Cm Urry, J Silverman, V Mainieri, G Hasinger, R Griffiths, M Carollo, H Hao, L Guzzo, A Blain, D Calzetti, C Carilli, P Capak, S Ettori, G Fabbiano, C Impey, S Lilly, B Mobasher, M Rich, M Salvato, Db Sanders, E Schinnerer, N Scoville, P Shopbell, Je Taylor, Y Taniguchi, M Volonteri

Astronomy Department Faculty Publication Series

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.5 deg2 of the COSMOS field (centered at 10 h , +02 o ) with an effective exposure of ~160 ks, and an outer 0.4 deg2 area with an effective exposure of ~80 ks. The limiting source detection depths are 1.9 × 10–16 erg cm–2 s–1 in the soft (0.5-2 keV) band, 7.3 × 10–16 erg cm–2 s–1 in the hard (2-10 keV) band, and 5.7 × 10–16 erg cm–2 s–1 in the full (0.5-10 keV) band. Here we describe the strategy, design, …

Uv Continuum Slope And Dust Obscuration From Z Similar To 6 To Z Similar To 2: The Star Formation Rate Density At High Redshift, R. J. Bouwens, G. D. Illingworth, M. Franx, R.-R. Chary, G. R. Meurer, C. J. Conselice, H. Ford, M. Giavalisco, P. Van Dokkum

Astronomy Department Faculty Publication Series

We provide a systematic measurement of the rest-frame UV continuum slope β over a wide range in redshift (z ∼ 2–6) and rest-frame UV luminosity (0.1 L*z = 3 to 2 L*z = 3) to improve estimates of the star formation rate (SFR) density at high redshift. We utilize the deep optical and infrared data (Advanced Camera for Surveys/NICMOS) over the Chandra Deep Field-South and Hubble Deep Field-North Great Observatories Origins Deep Survey fields, as well as the UDF for our primary UBVi "dropout" Lyman Break Galaxy sample. We also use strong lensing clusters to …

Deep U Band And R Imaging Of Goods-South: Observations, Data Reduction And First Results, M Nonino, M Dickinson, P Rosati, A Grazian, N Reddy, S Cristiani, M Giavalisco, H Kuntschner, E Vanzella, E Daddi, Rae Fosbury, C Cesarsky

Astronomy Department Faculty Publication Series

We present deep imaging in the U band covering an area of 630 arcmin2 centered on the southern field of the Great Observatories Origins Deep Survey (GOODS). The data were obtained with the VIMOS instrument at the European Southern Observatory (ESO) Very Large Telescope. The final images reach a magnitude limit Ulim ≈ 29.8 (AB, 1σ, in a 1'' radius aperture), and have good image quality, with full width at half-maximum ≈08. They are significantly deeper than previous U-band images available for the GOODS fields, and better match the sensitivity of other multiwavelength GOODS photometry. The deeper U …

Spectroscopic Observations Of Lyman Break Galaxies At Redshifts Similar To 4, 5, And 6 In The Goods-South Field, E Vanzella, M Giavalisco, M Dickinson, S Cristiani, M Nonino, H Kuntschner, P Popesso, P Rosati, A Renzini, D Stern, C Cesarsky, Hc Ferguson, Rae Fosbury

Astronomy Department Faculty Publication Series

We report on observations of Lyman-break galaxies (LBGs) selected from the Great Observatories Origins Deep Survey at mean redshift z~4, 5 and 6, obtained with FORS2 spectrograph at the ESO-VLT.This program has yielded spectroscopic identifications for 114 galaxies of which 51 are at z~4, 31 at z~5, and 32 at z~6. The adopted selection criteria are effective, identifying galaxies at the expected redshift with minimal foreground contamination. Once selection effects are properly accounted for, the rest-frame UV spectra of the higher-redshift LBGs appear to be similar to their counterparts at z~3. As at z~3, LBGs at z~4 and z~5 show …

The Growth Of Central And Satellite Galaxies In Cosmological Smoothed Particle Hydrodynamics Simulations, V Simha, Dh Weinberg, R Dave, Oy Gnedin, N Katz, D Keres

Astronomy Department Faculty Publication Series

We examine the accretion and merger histories of central and satellite galaxies in a smoothed particle hydrodynamics (SPH) cosmological simulation that resolves galaxies down to 7 × 10⁹ M_⊙. Most friends-of-friends haloes in the simulation have a distinct central galaxy, typically 2–5 times more massive than the most massive satellite. As expected, satellites have systematically higher assembly redshifts than central galaxies of the same baryonic mass, and satellites in more massive haloes form earlier. However, contrary to the simplest expectations, satellite galaxies continue to accrete gas and convert it to stars; the gas accretion declines steadily over …

Aztec Millimetre Survey Of The Cosmos Field - Ii. Source Count Overdensity And Correlations With Large-Scale Structure, Je Austermann, I Aretxaga, Dh Hughes, Y Kang, S Kim, Jd Lowenthal, Ta Perera, Db Sanders, Ks Scott, N Scoville, Gw Wilson, Min Yun

Astronomy Department Faculty Publication Series

We report an overdensity of bright submillimetre galaxies (SMGs) in the 0.15 deg² AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z≲ 1.1. This portion of the COSMOS field shows a ∼3σ overdensity of robust SMG detections when compared to a background, or ‘blank-field’, population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG overdensity is most significant in the number of very bright detections (14 sources with measured fluxes S_{1.1 mm} > 6 mJy), which is entirely incompatible with sample variance within our adopted …

Galaxies In A Simulated Lambda Cdm Universe - Ii. Observable Properties And Constraints On Feedback, D Keres, N Katz, R Dave, M Fardal, Dh Weinberg

Astronomy Department Faculty Publication Series

We compare the properties of galaxies that form in a cosmological simulation without strong feedback to observations of the z= 0 galaxy population. We confirm previous findings that models without strong feedback overproduce the observed galaxy baryonic mass function, especially at the low- and high-mass extremes. Through post-processing we investigate what kinds of feedback would be required to reproduce the statistics of observed galaxy masses and star formation rates. To mimic an extreme form of ‘preventive’ feedback, such as a highly efficient active galactic nucleus ‘radio mode’, we remove all baryonic mass that was originally accreted from shock-heated gas …

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 …

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 …

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 …

Fluctuations In Finite N Equilibrium Stellar Systems, Martin D. Weinberg

Astronomy Department Faculty Publication Series

Gravitational amplification of Poisson noise in stellar systems is important on large scales. For example, it increases the dipole noise power by roughly a factor of six and the quadrupole noise by 50% for a King model profile. The dipole noise is amplified by a factor of fifteen for the core-free Hernquist model. The predictions are computed using the dressed-particle formalism of Rostoker & Rosenbluth (1960) and are demonstrated by n-body simulation. This result implies that a collisionless n-body simulation is impossible; The fluctuation noise which causes relaxation is an intrinic part of self gravity. In other words, eliminating two-body …