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2003

Astronomy Department Faculty Publication Series

Articles 1 - 22 of 22

Full-Text Articles in Physical Sciences and Mathematics

The Optical And Near-Infrared Properties Of Galaxies. I. Luminosity And Stellar Mass Functions, Ef Bell, Dh Mcintosh, N Katz, Md Weinberg Jan 2003

The Optical And Near-Infrared Properties Of Galaxies. I. Luminosity And Stellar Mass Functions, Ef Bell, Dh Mcintosh, N Katz, Md Weinberg

Astronomy Department Faculty Publication Series

We use a large sample of galaxies from the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to calculate galaxy luminosity and stellar mass functions in the local universe. We estimate corrections for passband shifting and galaxy evolution, as well as present-day stellar mass-to-light (M/L) ratios, by fitting the optical-near-infrared galaxy data with simple models. Accounting for the 8% galaxy overdensity in the SDSS early data release region, the optical and near-infrared luminosity functions we construct for this sample agree with most recent literature optical and near-infrared determinations within the uncertainties. We argue that 2MASS …

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The Clustering Dipole Of The Local Universe From The Two Micron All Sky Survey, Ah Maller, Dh Mcintosh, N Katz, Md Weinberg Jan 2003

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 …

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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 Jan 2003

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 …

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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 Jan 2003

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, …

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On The Relationship Between Cooling Flows And Bubbles, Ig Mccarthy, A Babul, N Katz, Ml Balogh Jan 2003

On The Relationship Between Cooling Flows And Bubbles, Ig Mccarthy, A Babul, N Katz, Ml Balogh

Astronomy Department Faculty Publication Series

A common feature of the X-ray bubbles observed in Chandra images of some "cooling flow" clusters is that they appear to be surrounded by bright, cool shells. Temperature maps of a few nearby luminous clusters reveal that the shells consist of the coolest gas in the clusters—much cooler than the surrounding medium. Using simple models, we study the effects of this cool emission on the inferred cooling flow properties of clusters. We find that the introduction of bubbles into model clusters that do not have cooling flows results in temperature and surface brightness profiles that resemble those seen in nearby …

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The Influence Of Omega(B) On High-Redshift Structure, Jp Gardner, N Katz, L Hernquist, Dh Weinberg Jan 2003

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), …

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The Canada-Uk Deep Submillimeter Survey. Vii. Optical And Near-Infrared Identifications For The 14 Hour Field, Tma Webb, Sj Lilly, Dl Clements, S Eales, Min Yun, M Brodwin, L Dunne, Wk Gear Jan 2003

The Canada-Uk Deep Submillimeter Survey. Vii. Optical And Near-Infrared Identifications For The 14 Hour Field, Tma Webb, Sj Lilly, Dl Clements, S Eales, Min Yun, M Brodwin, L Dunne, Wk Gear

Astronomy Department Faculty Publication Series

We present the multiwavelength identifications for 23 sources in the Canada-UK Deep Submillimeter Survey (CUDSS) 14h field. The identifications have been selected on the basis of radio and near-infrared data, and we argue that, to our observational limits, both are effective at selecting the correct counterparts of the SCUBA sources. We discuss the properties of these identifications and find that they are very red in near-infrared color, with many classified as extremely red objects, and show disturbed morphologies. Using the entire CUDSS catalog of 50 sources, we use a combination of spectroscopic redshifts (four objects), 1.4 GHz : 850 …

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Supernova Remnant Crossing A Density Jump: A Thin-Shell Model, Y Chen, F Zhang, Rm Williams, Qd Wang Jan 2003

Supernova Remnant Crossing A Density Jump: A Thin-Shell Model, Y Chen, F Zhang, Rm Williams, Qd Wang

Astronomy Department Faculty Publication Series

The environments of supernova explosions are often inhomogeneous, and there may be jumps in their density structure. We have developed a semianalytic model under the thin-shell approximation for supernova remnants that evolve crossing a density jump in the ambient medium. The generic evolutionary relations are presented for the blast wave after impacting on a cavity wall, which may be produced by the energetic stellar wind from the supernova progenitor. The relations can also be extended to the case in which the blast waves break out from a dense cloud if a different density contrast is used. This model is applied …

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Chandra Observation Of The Edge-On Galaxy Ngc 3556 (M108): Violent Galactic Disk-Halo Interaction Revealed, Qd Wang, T Chaves, Ja Irwin Jan 2003

Chandra Observation Of The Edge-On Galaxy Ngc 3556 (M108): Violent Galactic Disk-Halo Interaction Revealed, Qd Wang, T Chaves, Ja Irwin

Astronomy Department Faculty Publication Series

We present a 60 ks Chandra ACIS-S observation of the isolated edge-on spiral galaxy NGC 3556, together with a multiwavelength analysis of various discrete X-ray sources and diffuse X-ray features. Among 33 discrete X-ray sources detected within the IB = 25 mag arcsec-2 isophote ellipse of the galaxy, we identify a candidate for the galactic nucleus, an ultraluminous X-ray source that might be an accreting intermediate-mass black hole, a possible X-ray binary with a radio counterpart, and two radio-bright giant H II regions. We detect large amounts of extraplanar diffuse X-ray emission, which extend about 10 kpc radially …

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The Lyman-Alpha Forest As A Cosmological Tool, Dh Weinberg, R Dave, N Katz, J Kollmeier Jan 2003

The Lyman-Alpha Forest As A Cosmological Tool, Dh Weinberg, R Dave, N Katz, J Kollmeier

Astronomy Department Faculty Publication Series

We review recent developments in the theory of the Ly forest and their implications for the role of the forest as a test of cosmological models. Simulations predict a relatively tight correlation between the local Ly optical depth and the local gas or dark matter density. Statistical properties of the transmitted flux can constrain the amplitude and shape of the matter power spectrum at high redshift, test the assumption of Gaussian initial conditions, and probe the evolution of dark energy by measuring the Hubble parameter H(z). Simulations predict increased Ly absorption in the vicinity of galaxies, but …

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A Survey Of 557 Ghz Water Vapor Emission In The Ngc 1333 Molecular Cloud, Ea Bergin, Mj Kaufman, Gj Melnick, Ronald L. Snell, Je Howe Jan 2003

A Survey Of 557 Ghz Water Vapor Emission In The Ngc 1333 Molecular Cloud, Ea Bergin, Mj Kaufman, Gj Melnick, Ronald L. Snell, Je Howe

Astronomy Department Faculty Publication Series

Using NASA's Submillimeter Wave Astronomy Satellite (SWAS), we have examined the production of water in quiescent and shocked molecular gas through a survey of the 556.936 GHz 110-101 transition of ortho-H2O in the NGC 1333 molecular core. These observations reveal broad emission lines associated with the IRAS 2, IRAS 4, IRAS 7, and HH 7-11 outflows. Toward three positions we detect narrow (Δv ~ 2-3 km s-1) emission lines clearly associated with the ambient gas. The SWAS observations, with a resolution of ~4', are supplemented with observations from the Infrared …

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How Do Galaxies Get Their Gas?, N Katz, D Keres, R Dave, Dh Weinberg Jan 2003

How Do Galaxies Get Their Gas?, N Katz, D Keres, R Dave, Dh Weinberg

Astronomy Department Faculty Publication Series

We examine the temperature history of gas accreted by forming galaxies in smoothed particle hydrodynamics simulations. About half of the gas follows the track expected in the conventional picture of galaxy formation, shock heating to roughly the virial temperature of the galaxy potential well (T∼ 106 K for a Milky Way type galaxy) before cooling, condensing and forming stars. However, the other half radiates its acquired gravitational energy at much lower temperatures, typically T < 105 K, and the histogram of maximum gas temperatures is clearly bimodal. The ‘cold mode’ of gas accretion dominates for low-mass galaxies (baryonic …

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Lyman Break Galaxies And The Ly Alpha Forest, Ja Kollmeier, Dh Weinberg, R Dave, N Katz Jan 2003

Lyman Break Galaxies And The Ly Alpha Forest, Ja Kollmeier, Dh Weinberg, R Dave, N Katz

Astronomy Department Faculty Publication Series

We use hydrodynamic cosmological simulations to predict correlations between Lyα forest absorption and the galaxy distribution at redshift z 3. The probability distribution function (PDF) of Lyα flux decrements shifts systematically toward higher values in the vicinity of galaxies, reflecting the overdense environments in which these galaxies reside. The predicted signal remains strong in spectra smoothed over 50-200 km s-1, allowing tests with moderate-resolution quasar spectra. The strong bias of high-redshift galaxies toward high-density regions imprints a clear signature on the flux PDF, but the predictions are not sensitive to galaxy baryon mass or star formation rate, and …

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A Two Micron All Sky Survey View Of The Sagittarius Dwarf Galaxy. I. Morphology Of The Sagittarius Core And Tidal Arms, Sr Majewski, Mf Skrutskie, Md Weinberg, Jc Ostheimer Jan 2003

A Two Micron All Sky Survey View Of The Sagittarius Dwarf Galaxy. I. Morphology Of The Sagittarius Core And Tidal Arms, Sr Majewski, Mf Skrutskie, Md Weinberg, Jc Ostheimer

Astronomy Department Faculty Publication Series

We present the first all-sky view of the Sagittarius (Sgr) dwarf galaxy mapped by M-giant star tracers detected in the complete Two Micron All Sky Survey (2MASS). Near-infrared photometry of Sgr's prominent M-giant population permits an unprecedentedly clear view of the center of Sgr. The main body is fitted with a King profile of limiting major-axis radius 30°—substantially larger than previously found or assumed—beyond which is a prominent break in the density profile from stars in the Sgr tidal tails; thus the Sgr radial profile resembles that of Galactic dwarf speroidal (dSph) satellites. Adopting traditional methods for analyzing dSph light …

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Investigating The Long-Term Evolution Of Galaxies: Noise, Cuspy Halos And Bars, Md Weinberg Jan 2003

Investigating The Long-Term Evolution Of Galaxies: Noise, Cuspy Halos And Bars, Md Weinberg

Astronomy Department Faculty Publication Series

I review the arguments for the importance of halo structure in driving galaxy evolution and coupling a galaxy to its environment. We begin with a general discussion of the key dynamics and examples of structure dominated by modes. We find that simulations with large numbers of particles (N ≳ 106) are required to resolve the dynamics. Finally, I will describe some new results which demonstrates that a disk bar can produce cores in a cuspy CDM dark-matter profile within a gigayear. An inner Lindblad-like resonance couples the rotating bar to halo orbits at all radii through the cusp, rapidly flattening …

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A First Estimate Of The Baryonic Mass Function Of Galaxies, Ef Bell, Dh Mcintosh, N Katz, Md Weinberg Jan 2003

A First Estimate Of The Baryonic Mass Function Of Galaxies, Ef Bell, Dh Mcintosh, N Katz, Md Weinberg

Astronomy Department Faculty Publication Series

We estimate the baryonic (stellar+cold gas) mass function of galaxies in the local universe by assigning a complete sample of Two Micron All Sky Survey and Sloan Digital Sky Survey galaxies a gas fraction based on a statistical sample of the entire population, under the assumption of a universally applicable stellar initial mass function. The baryonic mass function is similar to the stellar mass function at the high-mass end and has a reasonably steep faint-end slope owing to the typically high cold gas fractions and low stellar mass-to-light ratios characteristic of low-mass galaxies. The Schechter function fit parameters are phi*h-3 …

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The Galaxy Proximity Effect In The Lyalpha Forest, J Kollmeier, Dh Weinberg, R Dave, N Katz Jan 2003

The Galaxy Proximity Effect In The Lyalpha Forest, J Kollmeier, Dh Weinberg, R Dave, N Katz

Astronomy Department Faculty Publication Series

Hydrodynamic cosmological simulations predict that the average opacity of the Ly forest should increase in the neighborhood of galaxies because galaxies form in dense environments. Recent observations (Adelberger et al. [1]) confirm this expectation at large scales, but they show a decrease of absorption at comoving separations r 1h–1 Mpc. We show that this discrepancy is statistically significant, especially for the innermost data point at r 0.5h–1, even though this data point rests on three galaxy-quasar pairs. Galaxy redshift errors of the expected magnitude are insufficient to resolve the conflict. Peculiar velocities allow gas at …

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Probing O Vi Emission In The Halos Of Edge-On Spiral Galaxies, B Otte, Em Murphy, Jc Howk, Qd Wang, Wr Oegerle, Kr Sembach Jan 2003

Probing O Vi Emission In The Halos Of Edge-On Spiral Galaxies, B Otte, Em Murphy, Jc Howk, Qd Wang, Wr Oegerle, Kr Sembach

Astronomy Department Faculty Publication Series

We have used the Far Ultraviolet Spectroscopic Explorer to search for O VI λλ1031.926, 1037.617 emission in the halos of the edge-on spiral galaxies NGC 4631 and NGC 891. In NGC 4631, we detected O VI in emission toward a soft X-ray bubble above a region containing numerous Hα arcs and filaments. The line-of-sight component of the motion of the O VI gas appears to match the underlying disk rotation. The observed O VI luminosities can account for 0.2%-2% of the total energy input from supernovae (assuming a full O VI- emitting halo) and yield mass flux cooling rates between …

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Nonnuclear Hyper/Ultraluminous X-Ray Sources In The Starbursting Cartwheel Ring Galaxy, Y Gao, Qd Wang, Pn Appleton, Ra Lucas Jan 2003

Nonnuclear Hyper/Ultraluminous X-Ray Sources In The Starbursting Cartwheel Ring Galaxy, Y Gao, Qd Wang, Pn Appleton, Ra Lucas

Astronomy Department Faculty Publication Series

We report the Chandra/ACIS-S detection of more than 20 ultraluminous X-ray sources (ULXs; L0.5-10 keV 3 × 1039 ergs s-1) in the Cartwheel collisional ring galaxy system, of which over a dozen are located in the outer active star-forming ring. A remarkable hyperluminous X-ray source (HLX; L0.5-10 keV 1041 ergs s-1 assuming isotropic radiation), which dominates the X-ray emission from the Cartwheel ring, is located in the same segment of the ring as most ULXs. These powerful H/ULXs appear to be coincident with giant H II region complexes, young star clusters, and …

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The Origin Of The Dust Arch In The Halo Of Ngc 4631: An Expanding Superbubble?, Cl Taylor, Qd Wang Jan 2003

The Origin Of The Dust Arch In The Halo Of Ngc 4631: An Expanding Superbubble?, Cl Taylor, Qd Wang

Astronomy Department Faculty Publication Series

We study the nature and the origin of the dust arch in the halo of the edge-on galaxy NGC 4631 detected by Neininger & Dumke. We present CO observations made using the new on-the-fly mapping mode with the Five College Radio Astronomy Observatory 14 m telescope and find no evidence for CO emission associated with the dust arch. Our examination of previously published H I data shows that, if previous assumptions about the dust temperature and gas/dust ratio are correct, then there must be molecular gas associated with the arch, below our detection threshold. If this is true, then the …

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Structure Of Bright 2mass Galaxies: 2d Fits To The K-S-Band Surface Brightness Profiles, Dh Mcintosh, Ah Maller, N Katz, Md Weinberg Jan 2003

Structure Of Bright 2mass Galaxies: 2d Fits To The K-S-Band Surface Brightness Profiles, Dh Mcintosh, Ah Maller, 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 obtaining a detailed understanding of the galaxies populating our local (z<0.1) Universe. A full characterization of the physical structure of nearby galaxies is essential for theoretical and observational studies of galaxy evolution and structure formation. We have begun a quantified description of the internal structure and morphology of 10,000 bright (10<11) 2MASS galaxies through multi-component model fits to the 2D surface brightness profiles using GIM2D. From our initial Monte Carlo tests on 77 galaxies drawn at random from the RC3, we find that the model derived structural parameter errors due to sky uncertainies are typically less than 10%.

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The Chandra Detection Of Galactic Center X-Ray Features G359.89−0.08 And G359.54+0.18, Fj Lu, Qd Wang, Cc Lang Jan 2003

The Chandra Detection Of Galactic Center X-Ray Features G359.89−0.08 And G359.54+0.18, Fj Lu, Qd Wang, Cc Lang

Astronomy Department Faculty Publication Series

We report the detection of two elongated X-ray features, G359.89-0.08 and G359.54+0.18, in the Galactic center (GC) region using the Chandra X-Ray Observatory. G359.89-0.08 is an elongated X-ray feature located ~2' in projection south of the center of the Galaxy, Sgr A*. This X-ray feature source is partially coincident with a slightly curved ("wisplike") nonthermal radio source. The X-ray spectrum of G359.89-0.08 can best be characterized as nonthermal, with a photon index of 2. The morphological and spectral characteristics of the X-ray and radio emission associated with G359.89-0.08 are best interpreted as the synchrotron emission from a ram pressure–confined …

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