Papers by Dennis Zaritsky
Arxiv preprint arXiv: …, 2009
1 INAFOsservatorio Astronomico di Padova, Italy 2 University of Nottingham, UK 3 Ecole Polytechni... more 1 INAFOsservatorio Astronomico di Padova, Italy 2 University of Nottingham, UK 3 Ecole Polytechnique Federale de Lausanne, Switzerland 4 Institute for Astronomy, Edimburgh, UK 5 Ohio University, Athens, USA 6 University of Washington, Seattle, USA 7 INAFOsservatorio ...
The Astrophysical Journal Supplement Series, 2015
The Spitzer Survey of Stellar Structure in Galaxies (S 4 G) is the largest available database of ... more The Spitzer Survey of Stellar Structure in Galaxies (S 4 G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S 4 G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de Vaucouleurs (1959) morphology, modified to include recognition of other features such as inner, outer, and nuclear lenses, nuclear rings, bars, and disks, spheroidal galaxies, X patterns and box/peanut structures, OLR subclass outer rings and pseudorings, bar ansae and barlenses, parallel sequence late-types, thick disks, and embedded disks in 3D early-type systems. We show that our CVRHS classifications are internally consistent, and that nearly half of the S 4 G sample consists of extreme late-type systems (mostly bulgeless, pure disk galaxies) in the range Scd-Im. The most common family classification for mid-IR types S0/a to Sc is SA while that for types Scd to Sm is SB. The bars in these two type domains are very different in mid-IR structure and morphology. This paper examines the bar, ring, and type classification fractions in the sample, and also includes several montages of images highlighting the various kinds of "stellar structures" seen in mid-IR galaxy morphology.
The Astronomical Journal, 1998
We measure the extent of 100µm galactic emission in two independent galaxy samples using the IRAS... more We measure the extent of 100µm galactic emission in two independent galaxy samples using the IRAS 100µm Sky Survey images and constrain the distribution of dust at large ( ∼ < 30 kpc) radii. The first sample consists of 90 nearby (v < 6000 km/s) galaxies from the RC3 catalog with similar angular sizes and absolute luminosities (5 ′ ≤ D 25 ≤ 10 ′ and −22.5 ≤ M B ≤ − 18) that are isolated in the 100µm images. The second sample consists of 24 local galaxies (v < 1500 km/s, 10 ′ ≤ D 25 ≤ 30 ′ ). We rescale the 100µm images of these galaxies using their optical diameters, D 25 , rotate the images using their optical major axis position angle, construct the mean and median image, and rebin the final images into polar coordinates to study the 100µm emission as a function of radius and azimuthal angle. We find that the 100µm emission extends at least to radii of 27 kpc (2σ detection) for the typical galaxy in the 5 ′ − 10 ′ sample and to 21 kpc (2σ detection) in the 10 ′ − 30 ′ sample (H 0 =75 km/s/Mpc). In both samples, the emission is preferentially elongated along the optical major axis. We fit an exponential to the 100µm emission along the major axis and measure a scale length of 2.5 ± 0.8 kpc (90% confidence interval). Using a simple model that relates the far-IR emission to the stellar distribution, we examine the range of acceptable dust mass distributions allowed by our data and conclude that the dust is more extended than the starlight.
Monthly Notices of the Royal Astronomical Society, 2015
We identify some of the most HI massive and fastest rotating disk galaxies in the local universe ... more We identify some of the most HI massive and fastest rotating disk galaxies in the local universe with the aim of probing the processes that drive the formation of these extreme disk galaxies. By combining data from the Cosmic Flows project, which has consistently reanalyzed archival galaxy HI profiles, and 3.6µm photometry obtained with the Spitzer Space Telescope, with which we can measure stellar mass, we use the baryonic Tully-Fisher (BTF) relationship to explore whether these massive galaxies are distinct. We discuss several results, but the most striking is the systematic offset of the HI-massive sample above the BTF. These galaxies have both more gas and more stars in their disks than the typical disk galaxy of similar rotational velocity. The "condensed" baryon fraction, f C , the fraction of the baryons in a dark matter halo that settle either as cold gas or stars into the disk, is twice as high in the HImassive sample than typical, and almost reaches the universal baryon fraction in some cases, suggesting that the most extreme of these galaxies have little in the way of a hot baryonic component or cold baryons distributed well outside the disk. In contrast, the star formation efficiency, measured as the ratio of the mass in stars to that in both stars and gas, shows no difference between the HI-massive sample and the typical disk galaxies. We conclude that the star formation efficiency is driven by an internal, self-regulating process, while f C is affected by external factors. Neither the morphology nor the star formation rate of these galaxies is primarily determined by either their dark or stellar mass. We also found that the most massive HI detected galaxies are located preferentially in filaments. We present the first evidence of an environmental effect on galaxy evolution using a dynamical definition of a filament.
Monthly Notices of the Royal Astronomical Society, 2014
ABSTRACT We present a catalogue and images of visually detected features, such as asymmetries, ex... more ABSTRACT We present a catalogue and images of visually detected features, such as asymmetries, extensions, warps, shells, tidal tails, polar rings, and obvious signs of mergers or interactions, in the faint outer regions (at and outside of R25) of nearby galaxies. This catalogue can be used in future quantitative studies that examine galaxy evolution due to internal and external factors. We are able to reliably detect outer region features down to a brightness level of 0.03 MJy sr−1 pixel−1 at 3.6 μm in the Spitzer Survey of Stellar Structure in Galaxies (S4G). We also tabulate companion galaxies. We find asymmetries in the outer isophotes in 22 ± 1 per cent of the sample. The asymmetry fraction does not correlate with galaxy classification as an interacting galaxy or merger remnant, or with the presence of companions. We also compare the detected features to similar features in galaxies taken from cosmological zoom re-simulations. The simulated images have a higher fraction (33 per cent) of outer disc asymmetries, which may be due to selection effects and an uncertain star formation threshold in the models. The asymmetries may have either an internal (e.g. lopsidedness due to dark halo asymmetry) or external origin.
Monthly Notices of the Royal Astronomical Society, 2014
We study the surface brightness profiles of disc galaxies in the 3.6 µm images from the Spitzer S... more We study the surface brightness profiles of disc galaxies in the 3.6 µm images from the Spitzer Survey of Stellar Structure in Galaxies (S 4 G) and K s -band images from the Near Infrared S0-Sa galaxy Survey (NIRS0S). We particularly connect properties of single exponential (type I), downbending double exponential (type II), and upbending double exponential (type III) disc profile types, to structural components of galaxies by using detailed morphological classifications, and size measurements of rings and lenses. We also study how the local environment of the galaxies affects the profile types by calculating parameters describing the environmental density and the tidal interaction strength. We find that in majority of type II profiles the break radius is connected with structural components such as rings, lenses, and spirals. The exponential disc sections of all three profile types, when considered separately, follow the disc scaling relations. However, the outer discs of type II, and the inner discs of type III, are similar in scalelength to the single exponential discs. Although the different profile types have similar mean environmental parameters, the scalelengths of the type III profiles show a positive correlation with the tidal interaction strength.
Astrophysics and Space Science Library, 1994
We present a pilot study on the origin and assembly history of the ICL for four galaxy clusters a... more We present a pilot study on the origin and assembly history of the ICL for four galaxy clusters at 0.44 ≤ z ≤ 0.57 observed with the Hubble Space Telescope from the Cluster Lensing and Supernova Survey with Hubble (CLASH) sample. Using this sample of CLASH clusters we set an empirical limit on the amount of scatter in ICL surface brightness profiles of such clusters at z=0.5, a mean of 0.24 mag arcsec −2 for 10<r<110 kpc, and constrain the progenitor population and formation mechanism of the ICL by measuring the ICL surface brightness profile, the ICL colour and colour gradient, and the total ICL luminosity within the same radial range. This scatter is physical -it exceeds the observational errors, straightforward expectations from the range of cluster masses in our sample, and predictions based on published evolutionary models for the variance attributable to the redshift span of our sample. We associate the additional scatter with differences in ICL assembly process, formation epoch, and/or ICL content. Using stellar population synthesis models we transform the observed colours to metallicity. For three of the four clusters we find clear negative gradients that, on average, decrease from super solar in the central regions of the Brightest Cluster Galaxy (BCG) to sub-solar in the ICL, under the assumption that the age of the intracluster stars is >11 Gyrs. Such negative colour (and equivalently, metallicity) gradients can arise from tidal stripping of L* galaxies and/or the disruption of dwarf galaxies, but not major mergers with the BCG. We also find that the ICL at 110 kpc has a colour comparable to m*+2 red sequence galaxies, suggesting that out to this radius the ICL is dominated by stars liberated from galaxies with L>0.2 L*. Finally, we find ICL luminosities of 4-8 L* between 10<r<110 kpc for these clusters. Neither dwarf disruption or major mergers with the BCG alone can explain this level of luminosity and remain consistent with either the observed evolution in the faint end slope of the luminosity function or predictions for the number of BCG major mergers since z=1. Taken together, the results of this pilot study are suggestive of a formation history for these clusters in which the ICL is built-up by the stripping of >0.2L* galaxies, and disfavour significant contribution to the ICL by dwarf disruption or major mergers with the BCG.
We measure the baryons contained in both the stellar and hot-gas components for 12 galaxy cluster... more We measure the baryons contained in both the stellar and hot-gas components for 12 galaxy clusters and groups at z ∼ 0.1 with M = 1-5 × 10 14 M . This paper improves upon our previous work through the addition of XMM-Newton X-ray data, enabling measurements of the total mass and masses of each major baryonic component-intracluster medium, intracluster stars, and stars in galaxies-for each system. We recover a mean relation for the stellar mass versus halo mass, M ∝ M −0.52±0.04 500 , that is 1σ shallower than in our previous result. We confirm that the partitioning of baryons between the stellar and hot-gas components is a strong function of M 500 ; the fractions of total mass in stars and X-ray gas within a sphere of radius r 500 scale as f ∝ M −0.45±0.04 500 and f gas ∝ M 0.26±0.03 500 , respectively. We also confirm that the combination of the brightest cluster galaxy and intracluster stars is an increasingly important contributor to the stellar baryon budget in lower halo masses. Studies that fail to fully account for intracluster stars typically underestimate the normalization of the stellar baryon fraction versus M 500 relation by ∼25%. Our derived stellar baryon fractions are also higher, and the trend with halo mass weaker, than those derived from recent halo occupation distribution and abundance matching analyses. One difference from our previous work is the weak, but statistically significant, dependence here of the total baryon fraction upon halo mass: f bary ∝ M 0.16±0.04 500 . For M 500 2 × 10 14 , the total baryon fractions within r 500 are on average 18% below the universal value from the seven year Wilkinson Microwave Anisotropy Probe (WMAP) analysis, or 7% below for the cosmological parameters from the Planck analysis. In the latter case, the difference between the universal value and cluster baryon fractions is less than the systematic uncertainties associated with the M 500 determinations. The total baryon fractions exhibit significant scatter, particularly at M 500 < 2 × 10 14 M where they range from 60%-90%, or 65%-100%, of the universal value for WMAP7 and Planck, respectively. The ratio of the stellar-to-gas mass within r 500 (M /M gas ), a measure of integrated star-formation efficiency, strongly decreases with increasing M 500 . This relation is tight, with an implied intrinsic scatter of 12%. The fact that this relation remains tight at low mass implies that the larger scatter in the total baryon fractions at these masses arises from either true scatter in the total baryon content or observational scatter in M 500 rather than late-time physical processes such as redistribution of gas to beyond r 500 . If the scatter in the baryon content at low mass is physical, then our results imply that in this mass range, the integrated star-formation efficiency rather than the baryon fraction that is constant at fixed halo mass.
† The time delay distance D∆t ≡ (1+z d )D d Ds/D ds is a ratio of angular diameter distances (D; ... more † The time delay distance D∆t ≡ (1+z d )D d Ds/D ds is a ratio of angular diameter distances (D; s=source, d=deflector) and contains all the cosmological information (see, e.g., Treu 2010, for a description)
The degree to which outer dark matter halos of spiral galaxies rotate with the disk is sensitive ... more The degree to which outer dark matter halos of spiral galaxies rotate with the disk is sensitive to their accretion history and may be probed with associated satellite galaxies. We use the Steward Observatory Bok telescope to measure the sense of rotation of nearby isolated spirals and combine these data with those of their associated satellites (drawn from SDSS) to directly test predictions from numerical simulations. We aim to constrain models of galaxy formation by measuring the projected component of the halo angular momentum that is aligned with that of spiral galaxy disks, J z . We find the mean bulk rotation of the ensemble satellite system to be co-rotating with the disk with a velocity of 22 ± 13 km/s, in general agreement with previous observational studies and suggesting that galaxy disks could be formed by halo baryons collapsing by a factor of ≈ 10. We also find a prograde satellite fraction of 51%, and Jz of the satellite system to be positively correlated with the disk, albeit at low significance (2655 ± 2232 kpc km/s).
The Astrophysical Journal, 2015
ABSTRACT We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6$\mu$m photometry for &gt; 2000 gala... more ABSTRACT We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6$\mu$m photometry for &gt; 2000 galaxies, available for 90% of the S4G sample. We find a very tight &quot;GALEX Blue Sequence (GBS)&quot; in the (FUV-NUV) versus (NUV-[3.6]) color-color diagram which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale ($\tau$) and a degeneracy between $\tau$ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the &quot;GALEX Green Valley (GGV)&quot;. At the red end of the GBS, at (NUV-[3.6]) &gt; 5, we find a wider &quot;GALEX Red Sequence (GRS)&quot; mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by $\rm{M}_{[3.6]}$), since both massive ($M_{\star} &gt; 10^{11} M_{\odot}$) blue and red sequence galaxies are identified. The type that is proportionally more often found in the GGV are the S0-Sa&#39;s and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence on timescale of $10^{8}$years.
Galaxy clusters are the most massive quasi-equilibrium objects in the Universe and are the meetin... more Galaxy clusters are the most massive quasi-equilibrium objects in the Universe and are the meeting places of the cosmos. Their deep potential wells are dominated by unseen dark matter, but contain a cosmologically representative baryon fraction in the form of galaxies and intergalactic gas. These are trapped in a virialized state, with the gas heated to tens of millions of
We present the ESO Distant Cluster Survey (EDisCS), a survey of distant galaxy clusters between r... more We present the ESO Distant Cluster Survey (EDisCS), a survey of distant galaxy clusters between redshifts of z=0.4 and 0.8. Candidate clusters were chosen from among the brightest objects identified in the Las Campanas Distant Cluster Survey (LCDCS), half with estimated redshift zest ˜ 0.5 and half with zest ˜ 0.8. The sample of 20 clusters was confirmed using two-color
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Papers by Dennis Zaritsky