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Full-Text Articles in Physical Sciences and Mathematics
Wise X Supercosmos Photometric Redshift Catalog : 20 Million Galaxies Over 3pi Steradians., Maciej Bilicki, John A. Peacock, T. H. Jarrett, Michelle Cluver, Natasha Maddox, Michael J. I. Brown, Edward N. Taylor, Nigel C. Hambly, Aleksandra Solarz, Benne W. Holwerda, Ivan K. Baldry, Jon Loveday, Amanda J. Moffett, Andrew M. Hopkins, Simon P. Driver, Mehmet Alpaslan, Joss Bland-Hawthorn
Wise X Supercosmos Photometric Redshift Catalog : 20 Million Galaxies Over 3pi Steradians., Maciej Bilicki, John A. Peacock, T. H. Jarrett, Michelle Cluver, Natasha Maddox, Michael J. I. Brown, Edward N. Taylor, Nigel C. Hambly, Aleksandra Solarz, Benne W. Holwerda, Ivan K. Baldry, Jon Loveday, Amanda J. Moffett, Andrew M. Hopkins, Simon P. Driver, Mehmet Alpaslan, Joss Bland-Hawthorn
Benne Holwerda
We cross-match the two currently largest all-sky photometric catalogs—mid-infrared Wide-field Infrared Survey Explorer and SuperCOSMOS scans of UKST/POSS-II photographic plates—to obtain a new galaxy sample that covers 3π steradians. In order to characterize and purify the extragalactic data set, we use external GAMA and Sloan Digital Sky Survey spectroscopic information to define quasar and star loci in multicolor space, aiding the removal of contamination from our extended source catalog. After appropriate data cleaning, we obtain a deep wide-angle galaxy sample that is approximately 95% pure and 90% complete at high Galactic latitudes. The catalog contains close to 20 million galaxies …
Wise X Supercosmos Photometric Redshift Catalog : 20 Million Galaxies Over 3pi Steradians., Maciej Bilicki, John A. Peacock, T. H. Jarrett, Michelle Cluver, Natasha Maddox, Michael J. I. Brown, Edward N. Taylor, Nigel C. Hambly, Aleksandra Solarz, Benne W. Holwerda, Ivan K. Baldry, Jon Loveday, Amanda J. Moffett, Andrew M. Hopkins, Simon P. Driver, Mehmet Alpaslan, Joss Bland-Hawthorn
Wise X Supercosmos Photometric Redshift Catalog : 20 Million Galaxies Over 3pi Steradians., Maciej Bilicki, John A. Peacock, T. H. Jarrett, Michelle Cluver, Natasha Maddox, Michael J. I. Brown, Edward N. Taylor, Nigel C. Hambly, Aleksandra Solarz, Benne W. Holwerda, Ivan K. Baldry, Jon Loveday, Amanda J. Moffett, Andrew M. Hopkins, Simon P. Driver, Mehmet Alpaslan, Joss Bland-Hawthorn
Faculty Scholarship
We cross-match the two currently largest all-sky photometric catalogs—mid-infrared Wide-field Infrared Survey Explorer and SuperCOSMOS scans of UKST/POSS-II photographic plates—to obtain a new galaxy sample that covers 3π steradians. In order to characterize and purify the extragalactic data set, we use external GAMA and Sloan Digital Sky Survey spectroscopic information to define quasar and star loci in multicolor space, aiding the removal of contamination from our extended source catalog. After appropriate data cleaning, we obtain a deep wide-angle galaxy sample that is approximately 95% pure and 90% complete at high Galactic latitudes. The catalog contains close to 20 million galaxies …
The Photon Underproduction Crisis, Juna A. Kollmeier, David H. Weinberg, Benjamin D. Oppenheimer, Francesco Haardt, Neal S. Katz, Rameel A. Dave, Mark Fardal, Piero Madau, Charles Danforth, Amanda B. Ford, Molly S. Peeples, Joseph Mcewen
The Photon Underproduction Crisis, Juna A. Kollmeier, David H. Weinberg, Benjamin D. Oppenheimer, Francesco Haardt, Neal S. Katz, Rameel A. Dave, Mark Fardal, Piero Madau, Charles Danforth, Amanda B. Ford, Molly S. Peeples, Joseph Mcewen
Neal S. Katz
We examine the statistics of the low-redshift Lyα forest from smoothed particle hydrodynamic simulations in light of recent improvements in the estimated evolution of the cosmic ultraviolet background (UVB) and recent observations from the Cosmic Origins Spectrograph (COS). We find that the value of the metagalactic photoionization rate (ΓHI) required by our simulations to match the observed properties of the low-redshift Lyα forest is a factor of five larger than the value predicted by state-of-the art models for the evolution of this quantity. This mismatch in ΓHI results in the mean flux decrement of the Lyα forest being overpredicted by …
The Deep2 Galaxy Redshift Survey: Design, Observations, Data Reduction, And Redshifts, Jeffery A. Newman, Michael C. Cooper, Marc Davis, S. M. Faber, Alison L. Coil, Puragra Guhathakurta, David C. Koo, Andrew C. Phillips, Charlie Conroy, Aaron A. Dutton, Douglas P. Finkbeiner, Brian F. Gerke, David J. Rosario, Benjamin J. Weiner, Renbin Yan, Justin J. Harker, Susan A. Kassin, N. P. Konidaris, Kamson Lai, Darren S. Madgwick, K. G. Noeske, Gregory D. Wirth, A. J. Connolly, N. Kaiser, Evan N. Kirby, Brian C. Lemaux, Lihwai Lin, Jennifer M. Lotz, G. A. Luppino, C. Marinoni
The Deep2 Galaxy Redshift Survey: Design, Observations, Data Reduction, And Redshifts, Jeffery A. Newman, Michael C. Cooper, Marc Davis, S. M. Faber, Alison L. Coil, Puragra Guhathakurta, David C. Koo, Andrew C. Phillips, Charlie Conroy, Aaron A. Dutton, Douglas P. Finkbeiner, Brian F. Gerke, David J. Rosario, Benjamin J. Weiner, Renbin Yan, Justin J. Harker, Susan A. Kassin, N. P. Konidaris, Kamson Lai, Darren S. Madgwick, K. G. Noeske, Gregory D. Wirth, A. J. Connolly, N. Kaiser, Evan N. Kirby, Brian C. Lemaux, Lihwai Lin, Jennifer M. Lotz, G. A. Luppino, C. Marinoni
Physics and Astronomy Faculty Publications
We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ~ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = –20 at z ~ 1 via ~90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of RAB = 24.1. Objects with z ≲ 0.7 are readily …
The Laboca Survey Of The Extended Chandra Deep Field-South: Clustering Of Submillimetre Galaxies, Ryan C. Hickox, J. L. Wardlow, Ian Smail, A. D. Myers
The Laboca Survey Of The Extended Chandra Deep Field-South: Clustering Of Submillimetre Galaxies, Ryan C. Hickox, J. L. Wardlow, Ian Smail, A. D. Myers
Dartmouth Scholarship
We present a measurement of the spatial clustering of submillimetre galaxies (SMGs) at z = 1–3. Using data from the 870 μm LABOCA submillimetre survey of the Extended Chandra Deep Field South, we employ a novel technique to measure the cross-correlation between SMGs and galaxies, accounting for the full probability distributions for photometric redshifts of the galaxies. From the observed projected two-point cross-correlation function we derive the linear bias and characteristic dark matter halo masses for the SMGs. We detect clustering in the cross-correlation between SMGs and galaxies at the > 4σ level. Accounting for the clustering of galaxies from their …
In Search Of Empty Places: Voids In The Distribution Of Galaxies, Brian K. Bucklein
In Search Of Empty Places: Voids In The Distribution Of Galaxies, Brian K. Bucklein
Theses and Dissertations
We investigate several techniques to identify voids in the galaxy distribution of matter in the universe. We utilize galaxy number counts as a function of apparent magnitude and Wolf plots to search a two- or three-dimensional data set in a pencil-beam fashion to locate voids within the field of view. The technique is able to distinguish between voids that represent simply a decrease in density as well as those that show a build up of galaxies on the front or back side of the void. This method turns out to be primarily useable only at relatively short range (out to …
Mapping The Dark Matter From Uv Light At High Redshift: An Empirical Approach To Understand Galaxy Statistics, Kyoung-Soo Lee, Mauro Giavalisco, Charlie Conroy, Risa H. Wechsler, Henry C. Ferguson, Rachel S. Somerville, Mark E. Dickinson, Claudia M. Urry
Mapping The Dark Matter From Uv Light At High Redshift: An Empirical Approach To Understand Galaxy Statistics, Kyoung-Soo Lee, Mauro Giavalisco, Charlie Conroy, Risa H. Wechsler, Henry C. Ferguson, Rachel S. Somerville, Mark E. Dickinson, Claudia M. Urry
Astronomy Department Faculty Publication Series
We present a simple formalism to interpret the observations of two galaxy statistics, the UV luminosity function (LF) and two-point correlation functions for star-forming galaxies at z∼4, 5, and 6 in the context of Λ cold dark matter cosmology. Both statistics are the result of how star formation takes place in dark matter halos, and thus are used to constrain how UV light depends on halo properties, in particular halo mass. The two physical quantities we explore are the star formation duty cycle, and the range of UV luminosity that a halo of mass M can have (mean and …
The Nature Of Red Dwarf Galaxies, Y Wang, Xh Yang, Hj Mo, Fc Van Den Bosch, N Katz, A Pasquali, Dh Mcintosh, Sm Weinmann
The Nature Of Red Dwarf Galaxies, Y Wang, Xh Yang, Hj Mo, Fc Van Den Bosch, N Katz, A Pasquali, Dh Mcintosh, Sm Weinmann
Astronomy Department Faculty Publication Series
Using dark matter halos traced by galaxy groups selected from the Sloan Digital Sky Survey Data Release 4, we find that about 1/4 of the faint galaxies (0.1 Mr – 5log h> – 17.05, hereafter dwarfs) that are the central galaxies in their own halo are not blue and star forming, as expected in standard models of galaxy formation, but are red. In contrast, this fraction is about 1/2 for dwarf satellite galaxies. Many red dwarf galaxies are physically associated with more massive halos. In total, about ~45% of red dwarf galaxies reside in massive halos as satellites, …
Baryon Dynamics, Dark Matter Substructure, And Galaxies, Dh Weinberg, S Colombi, R Dave, N Katz
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 …
From Galaxy-Galaxy Lensing To Cosmological Parameters, J Yoo, Jl Tinker, Dh Weinberg, Z Zheng, N Katz, R Dave
From Galaxy-Galaxy Lensing To Cosmological Parameters, J Yoo, Jl Tinker, Dh Weinberg, Z Zheng, N Katz, R Dave
Astronomy Department Faculty Publication Series
Galaxy-galaxy lensing uses the weak distortion of background sources to measure the mean excess surface density profile, ΔΣ(r), around a sample of foreground lensing galaxies. We develop a method for combining ΔΣ(r) with the galaxy-galaxy correlation function ξgg(r) to constrain the matter density parameter Ωm and the matter fluctuation amplitude σ8, going beyond the linear biasing model to reach the level of accuracy demanded by current and future measurements. We adopt the halo occupation distribution (HOD) framework and test its applicability to this problem by examining the effects of …
The Galaxy Angular Correlation Functions And Power Spectrum From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
The Galaxy Angular Correlation Functions And Power Spectrum From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
Astronomy Department Faculty Publication Series
We calculate the angular correlation function of galaxies in the Two Micron All Sky Survey. We minimize the possible contamination by stars, dust, seeing, and sky brightness by studying their cross correlation with galaxy density and limiting the galaxy sample accordingly. We measure the correlation function at scales between 1' < θ < 18° using a half-million galaxies. We find that a best-fit power law to the correlation function has a slope of -0.79 ± 0.02 and an amplitude at 1° of 0.10 ± 0.01 in the range 1'-2fdg5. However, there are statistically significant oscillations around this power law. The largest oscillation occurs at about 0fdg8, corresponding to 700 h-1 kpc at the median redshift of our survey, as expected in halo occupation distribution descriptions of galaxy clustering. In addition, there is a break in the power-law shape of the correlation function at θ > 2fdg5. Our results are in good agreement with other measurements of the angular correlation function. We invert the angular correlation function using singular value decomposition to measure the three-dimensional power spectrum and find that it too is in good agreement with previous measurements. A dip seen in the power spectrum …
Theoretical Models Of The Halo Occupation Distribution: Separating Central And Satellite Galaxies, Z Zheng, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, N Katz, Cg Lacey
Theoretical Models Of The Halo Occupation Distribution: Separating Central And Satellite Galaxies, Z Zheng, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, N Katz, Cg Lacey
Astronomy Department Faculty Publication Series
The halo occupation distribution (HOD) describes the relation between galaxies and dark matter at the level of individual dark matter halos. The properties of galaxies residing at the centers of halos differ from those of satellite galaxies because of differences in their formation histories. Using a smoothed particle hydrodynamics (SPH) simulation and a semianalytic (SA) galaxy formation model, we examine the separate contributions of central and satellite galaxies to the HOD, more specifically to the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class. In agreement with earlier …
Interpreting The Relationship Between Galaxy Luminosity, Color, And Environment, Aa Berlind, Mr Blanton, Dw Hogg, Dh Weinberg, R Dave, Dj Eisenstein, N Katz
Interpreting The Relationship Between Galaxy Luminosity, Color, And Environment, Aa Berlind, Mr Blanton, Dw Hogg, Dh Weinberg, R Dave, Dj Eisenstein, N Katz
Astronomy Department Faculty Publication Series
We study the relationship between galaxy luminosity, color, and environment in a cosmological simulation of galaxy formation. Using a simple prescription to assign colors and luminosities to simulated galaxies, we compare the predicted relationship with that observed for SDSS galaxies and find that the model successfully predicts most of the qualitative features seen in the data, but also shows some interesting differences. Specifically, the simulation predicts that the local density around bright red galaxies is a strong increasing function of luminosity, but does not depend much on color at fixed luminosity. Moreover, we show that these trends are due to …
Simulation Of Soft X-Ray Emission Lines From The Missing Baryons, Tt Fang, Rac Croft, Wt Sanders, J Houck, R Dave, N Katz, Dh Weinberg, L Hernquist
Simulation Of Soft X-Ray Emission Lines From The Missing Baryons, Tt Fang, Rac Croft, Wt Sanders, J Houck, R Dave, N Katz, Dh Weinberg, L Hernquist
Astronomy Department Faculty Publication Series
We study the soft X-ray emission (0.1-1 keV) from the warm-hot intergalactic medium (WHIM) in a hydrodynamic simulation of a cold dark matter universe. Our main goal is to investigate how such emission can be explored with a combination of imaging and spectroscopy and to motivate future X-ray missions. We first present high-resolution images of the X-ray emission in several energy bands in which emission from different ion species dominates. We pick three different areas to study the high-resolution spectra of X-rays from the WHIM: (1) a galaxy group, (2) a filament, and (3) an underluminous region. By taking into …
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
The Oxford-Dartmouth Thirty Degree Survey - I. Observations And Calibration Of A Wide-Field Multiband Survey, Emily C. Macdonald, Paul Allen, Gavin Dalton, Leonidas A. Moustakas, Catherine Heymans, Edward Edmondso N, Chris Blake, Lee Clewley, Molly C. Hammell, Ed Olding, Lance Miller, Steve Rawlings, Jasper Wall, Gary Wegner, Christian Wolf
Dartmouth Scholarship
The Oxford–Dartmouth Thirty Degree Survey (ODTS) is a deep, wide, multiband imaging survey designed to cover a total of 30 deg2 in BV Ri′Z, with a subset of U- and K-band data, in four separate fields of 5–10 deg2 centred at 00:18:24 +34:52, 09:09:45 +40:50, 13:40:00 +02:30 and 16:39:30 +45:24. Observations have been made using the Wide Field Camera on the 2.5-m Isaac Newton Telescope (INT) in La Palma to average limiting depths (5σ Vega, aperture magnitudes) of U= 24.8, B= 25.6, V= 25.0, R= 24.6 and i′= …
Galaxy Clustering And Galaxy Bias In A Lambda Cdm Universe, Dh Weinberg, R Dave, N Katz, L Hernquist
Galaxy Clustering And Galaxy Bias In A Lambda Cdm Universe, Dh Weinberg, R Dave, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
We investigate galaxy clustering and the correlations between galaxies and mass in the ΛCDM cosmological model (inflationary cold dark matter with Ωm = 0.4, ΩΛ = 0.6, h = 0.65, n = 0.95, and σ8 = 0.8), using a large, smoothed particle hydrodynamics simulation (SPH; with 2 × 1443 particles in a 50 h-1 Mpc cube). Simulated galaxies can be unambiguously identified as clumps of stars and cold gas a few kpc to a few tens of kpc across, residing in extended halos of hot gas and dark matter; the space density of the resolved …
The Clustering Dipole Of The Local Universe From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
The Clustering Dipole Of The Local Universe From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg
Astronomy Department Faculty Publication Series
The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) provides a rich resource for investigating the galaxies populating the local universe. A full characterization of the large-scale clustering distribution is important for theoretical studies of structure formation. 2MASS offers an all-sky view of the local galaxy population at 2.15 μm, unbiased by young stellar light and minimally affected by dust. We use 2MASS to map the local distribution of galaxies, identifying the largest structures in the nearby universe. The inhomogeneity of these structures causes an acceleration on the Local Group of galaxies, which can …
X-Ray Absorption By The Low-Redshift Intergalactic Medium: A Numerical Study Of The Lambda Cold Dark Matter Model, Xl Chen, Dh Weinberg, N Katz, R Dave
X-Ray Absorption By The Low-Redshift Intergalactic Medium: A Numerical Study Of The Lambda Cold Dark Matter Model, Xl Chen, Dh Weinberg, N Katz, R Dave
Astronomy Department Faculty Publication Series
Using a hydrodynamic simulation of a cold dark matter universe with a cosmological constant, we investigate the "X-ray forest" absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM), at redshift z 0. In agreement with previous studies, we find that O VII and O VIII produce the strongest absorption features. The strong oxygen absorbers that might be detectable with Chandra or XMM-Newton arise in gas with T ~ 105.5-106.5 K and overdensities δ 100 that are characteristic of galaxy groups. Future X-ray missions could detect weaker oxygen absorption produced by gas with …
The Halo Occupation Distribution And The Physics Of Galaxy Formation, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, A Jenkins, N Katz, Cg Lacey
The Halo Occupation Distribution And The Physics Of Galaxy Formation, Aa Berlind, Dh Weinberg, Aj Benson, Cm Baugh, S Cole, R Dave, Cs Frenk, A Jenkins, N Katz, Cg Lacey
Astronomy Department Faculty Publication Series
The halo occupation distribution (HOD) describes the bias between galaxies and dark matter by specifying (1) the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class and (2) the relative spatial and velocity distributions of galaxies and dark matter within halos. We calculate and compare the HODs predicted by a smoothed particle hydrodynamics (SPH) simulation of a ΛCDM cosmological model (cold dark matter with a cosmological constant) and by a semianalytic galaxy formation model applied to the same cosmology. Although the two methods predict different galaxy mass functions, …
The Influence Of Omega(B) On High-Redshift Structure, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
The Influence Of Omega(B) On High-Redshift Structure, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We analyze high-redshift structure in three hydrodynamic simulations that have identical initial conditions and cosmological parameters and differ only in the value of the baryon density parameter, Ωb = 0.02, 0.05, and 0.125. Increasing Ωb does not change the fraction of baryons in the diffuse (unshocked) phase of the intergalactic medium, but it increases cooling rates and therefore transfers some baryons from the shocked intergalactic phase to the condensed phase associated with galaxies. Predictions of Lyα forest absorption are almost unaffected by changes in Ωb at velocity scales greater than 5 km s-1 (our resolution limit), …
Toward A Precise Measurement Of Matter Clustering: Ly Alpha Forest Data At Redshifts 2-4, Rac Croft, Dh Weinberg, M Bolte, S Burles, L Hernquist, N Katz, D Kirkman, D Tytler
Toward A Precise Measurement Of Matter Clustering: Ly Alpha Forest Data At Redshifts 2-4, Rac Croft, Dh Weinberg, M Bolte, S Burles, L Hernquist, N Katz, D Kirkman, D Tytler
Astronomy Department Faculty Publication Series
We measure the filling factor, correlation function, and power spectrum of transmitted flux in a large sample of Lyα forest spectra, comprised of 30 Keck HIRES spectra and 23 Keck LRIS spectra. We infer the linear matter power spectrum P(k) from the flux power spectrum PF(k), using an improved version of the method of Croft et al. that accounts for the influence of redshift-space distortions, nonlinearity, and thermal broadening on the shape of PF(k). The evolution of the shape and amplitude of P(k) over the redshift …
Comparing Simulations And Observations Of The Ly Alpha Forest. I. Methodology, Ce Petry, Cd Impey, N Katz, Dh Weinberg, Le Hernquist
Comparing Simulations And Observations Of The Ly Alpha Forest. I. Methodology, Ce Petry, Cd Impey, N Katz, Dh Weinberg, Le Hernquist
Astronomy Department Faculty Publication Series
We describe techniques for comparing spectra extracted from cosmological simulations and observational data, using the same methodology to link Lyα properties derived from the simulations with properties derived from observational data. The eventual goal is to measure the coherence or clustering properties of Lyα absorbers using observations of quasar pairs and groups. We quantify the systematic underestimate in opacity that is inherent in the continuum-fitting process of observed spectra over a range of resolution and signal-to-noise ratio (S/N). We present an automated process for detecting and selecting absorption features over the range of resolution and S/N of typical observational data …
High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz
High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz
Astronomy Department Faculty Publication Series
We use hydrodynamic cosmological simulations to predict the star formation properties of high-redshift galaxies (z = 2-6) in five variants of the inflationary cold dark matter scenario, paying particular attention to z = 3, the redshift of the largest "Lyman break galaxy" (LBG) samples. Because we link the star formation timescale to the local gas density, the rate at which a galaxy forms stars is governed mainly by the rate at which it accretes cooled gas from the surrounding medium. At z = 3, star formation in most of the simulated galaxies is steady on ~200 Myr timescales, and …
Comparing The Sfi Peculiar Velocities With The Pscz Gravity Field: A Velmod Analysis, E. Branchini, W. Freudling, L. N. Da Costa, C. S. Frenk, R. Giovanelli, M. P. Haynes, J. J. Salzer, G. Wegner, I. Zehavi
Comparing The Sfi Peculiar Velocities With The Pscz Gravity Field: A Velmod Analysis, E. Branchini, W. Freudling, L. N. Da Costa, C. S. Frenk, R. Giovanelli, M. P. Haynes, J. J. Salzer, G. Wegner, I. Zehavi
Dartmouth Scholarship
We compare the peculiar velocities derived from the I-band Tully–Fisher (TF) relation for 989 field spiral galaxies in the SFI catalogue with the predicted velocity field derived from the IRAS PSCz galaxy redshift survey. We assume linear gravitational instability theory and apply the maximum likelihood technique, VELMOD to SFI galaxies within a redshift cz LG =6000 km s−1. The resulting calibration of the TF relation is consistent with a previous, independent calibration for a similar sample of spirals residing in clusters. Our analysis provides an accurate estimate of the quantity βI ≡ Ωm0.6 …
Large-Scale Power Spectrum And Structures From The Enear Galaxy Peculiar Velocity Catalogue, S. Zaroubi, M. Bernardi, L. N. Da Costa, Y. Hoffman, M. V. Alonso, G. Wegner
Large-Scale Power Spectrum And Structures From The Enear Galaxy Peculiar Velocity Catalogue, S. Zaroubi, M. Bernardi, L. N. Da Costa, Y. Hoffman, M. V. Alonso, G. Wegner
Dartmouth Scholarship
We estimate the mass density fluctuations power spectrum (PS) on large scales by applying a maximum likelihood technique to the peculiar velocity data of the recently completed redshift—distance survey of early-type galaxies (hereafter ENEAR). Parametric cold dark matter (CDM)-like models for the PS are assumed, and the best-fitting parameters are determined by maximizing the probability of the model given the measured peculiar velocities of the galaxies, their distances and estimated errors. The method has been applied to CDM models with and without COBE normalization. The general results are in agreement with the high-amplitude power spectra found from similar analyses of …
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions - Vi. The Maximum-Likelihood Gaussian Algorithm, M. Colless, R. P. Saglia, D. Burstein, R. L. Davies, R. K. Mcmahan, G. Wegner
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions - Vi. The Maximum-Likelihood Gaussian Algorithm, M. Colless, R. P. Saglia, D. Burstein, R. L. Davies, R. K. Mcmahan, G. Wegner
Dartmouth Scholarship
The EFAR project is designed to measure the properties and peculiar motions of early-type galaxies in two distant regions. Here we describe the maximum-likelihood algorithm we developed to investigate the correlations between the parameters of the EFAR data base. One-, two- and three-dimensional Gaussian models are constructed to determine the mean value and intrinsic spread of the parameters, and the slopes and intrinsic parallel and orthogonal spread of the Mg2–Mgb′,Mg2–σ,Mgb′–σ relations, and the Fundamental Plane. In the latter case, the cluster peculiar velocities are also determined. We show that this method is superior to …
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions -- Vii. Peculiar Velocities And Bulk Motions, Matthew Colless, R. P. Saglia, David Burstein, Roger L. Davies, Robert K. Mcmahan Jr, Gary Wegner
The Peculiar Motions Of Early-Type Galaxies In Two Distant Regions -- Vii. Peculiar Velocities And Bulk Motions, Matthew Colless, R. P. Saglia, David Burstein, Roger L. Davies, Robert K. Mcmahan Jr, Gary Wegner
Dartmouth Scholarship
We present peculiar velocities for 85 clusters of galaxies in two large volumes at distances between 6000 and 15 000 km s−1 in the directions of Hercules-Corona Borealis and Perseus-Pisces-Cetus (the EFAR sample). These velocities are based on Fundamental Plane (FP) distance estimates for early-type galaxies in each cluster. We fit the FP using a maximum likelihood algorithm which accounts for both selection effects and measurement errors, and yields FP parameters with smaller bias and variance than other fitting procedures. We obtain a best-fitting FP with coefficients consistent with the best existing determinations. We measure the bulk motions of …
Hydrodynamic Simulation Of The Cosmological X-Ray Background, Rac Croft, T Di Matteo, L Hernquist, N Katz, Ma Fardal, Dh Weinberg
Hydrodynamic Simulation Of The Cosmological X-Ray Background, Rac Croft, T Di Matteo, L Hernquist, N Katz, Ma Fardal, Dh Weinberg
Astronomy Department Faculty Publication Series
We use a hydrodynamic simulation of an inflationary cold dark matter model with a cosmological constant to predict properties of the extragalactic X-ray background (XRB). We focus on emission from the intergalactic medium (IGM), with particular attention to diffuse emission from warm-hot gas that lies in relatively smooth filamentary structures between galaxies and galaxy clusters. We also include X-rays from point sources associated with galaxies in the simulation, and we make maps of the angular distribution of the emission. Although much of the X-ray luminous gas has a filamentary structure, the filaments are not evident in the simulated maps because …
Constraints On Cosmological Parameters From The Ly Alpha Forest Power Spectrum And Cobe Dmr, J Phillips, Dh Weinberg, Rac Croft, L Hernquist, N Katz, M Pettini
Constraints On Cosmological Parameters From The Ly Alpha Forest Power Spectrum And Cobe Dmr, J Phillips, Dh Weinberg, Rac Croft, L Hernquist, N Katz, M Pettini
Astronomy Department Faculty Publication Series
We combine COBE DMR measurements of cosmic microwave background (CMB) anisotropy with a recent measurement of the mass power spectrum at redshift z = 2.5 from Lyα forest data to derive constraints on cosmological parameters and test the inflationary cold dark matter (CDM) scenario of structure formation. By treating the inflationary spectral index n as a free parameter, we are able to find successful fits to the COBE and Lyα forest constraints in Ωm = 1 models with and without massive neutrinos and in low-Ωm models with and without a cosmological constant. Within each class of model, the …
Simulations Of Damped Ly Alpha And Lyman Limit Absorbers In Different Cosmologies: Implications For Structure Formation At High Redshift, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
Simulations Of Damped Ly Alpha And Lyman Limit Absorbers In Different Cosmologies: Implications For Structure Formation At High Redshift, Jp Gardner, N Katz, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We use hydrodynamic cosmological simulations to study damped Lyα (DLA) and Lyman limit (LL) absorption at redshifts z = 2-4 in five variants of the cold dark matter scenario: COBE-normalized (CCDM), cluster-normalized (SCDM), and tilted (n = 0.8) Ωm = 1 models, as well as open (OCDM) and flat (LCDM) Ωm = 0.4 models. Our standard simulations resolve the formation of dense concentrations of neutral gas in halos with circular velocity vc ≥ vc,res 140 km s-1 for Ωm = 1 and 90 km s-1 for Ωm = 0.4, …