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Full-Text Articles in Physical Sciences and Mathematics
Ongoing Assembly Of Massive Galaxies By Major Merging In Large Groups And Clusters From The Sdss, Dh Mcintosh, Yc Guo, J Hertzberg, N Katz, Hj Mo, Fc Van Den Bosch, Xh Yang
Ongoing Assembly Of Massive Galaxies By Major Merging In Large Groups And Clusters From The Sdss, Dh Mcintosh, Yc Guo, J Hertzberg, N Katz, Hj Mo, Fc Van Den Bosch, Xh Yang
Astronomy Department Faculty Publication Series
We investigate the incidence of major mergers creating massive (Mstar > 1011 M⊙) galaxies in present-day (z≤ 0.12) groups and clusters. Using a volume-limited sample of 845 groups with dark matter halo masses above 2.5 × 1013 M⊙, we isolate 221 galaxy pairs with ≤1.5 r-band magnitude differences, ≤30 kpc projected separations and combined masses above 1011 M⊙. We fit the r-band images of each pair as the line-of-sight projection of symmetric models and identify 38 mergers by the presence of residual asymmetric structure associated with …
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 …
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 …
On The Relationship Between Cooling Flows And Bubbles, Ig Mccarthy, A Babul, N Katz, Ml Balogh
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 …
X-Ray Scaling Relations Of Galaxy Groups In A Hydrodynamic Cosmological Simulation, R Dave, N Katz, Dh Weinberg
X-Ray Scaling Relations Of Galaxy Groups In A Hydrodynamic Cosmological Simulation, R Dave, N Katz, Dh Weinberg
Astronomy Department Faculty Publication Series
We examine the scalings of X-ray luminosity, temperature, and dark matter or galaxy velocity dispersion for galaxy groups in a ΛCDM cosmological simulation, which incorporates gravity, gas dynamics, radiative cooling, and star formation, but no substantial nongravitational heating. In agreement with observations, the simulated LX-σ and LX-TX relations are steeper than those predicted by adiabatic simulations or self-similar models, with LX σ4.4 and LX T for massive groups and significantly steeper relations below a break at σ 180 km s-1 (TX 0.7 keV). The TX-σ relation …
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 …
Perturbations Of Spherical Stellar Systems During Flyby Encounters, E Vesperini, Md Weinberg
Perturbations Of Spherical Stellar Systems During Flyby Encounters, E Vesperini, Md Weinberg
Astronomy Department Faculty Publication Series
We study the internal response of a galaxy to an unbound encounter and present a survey of orbital parameters covering typical encounters in different galactic environments. Overall, we conclude that relatively weak encounters by low-mass interloping galaxies can cause observable distortions in the primaries. The resulting asymmetries may persist long after the interloper is evident. We focus our attention on the production of structure in dark halos and in cluster elliptical galaxies. Any distortion produced in a dark halo can distort the embedded stellar disk, possibly leading to the formation of lopsided and warped disks. We show that distant encounters …
The Effects Of Gasdynamics, Cooling, Star Formation, And Numerical Resolution In Simulations Of Cluster Formation, Gf Lewis, A Babul, N Katz, T Quinn, L Hernquist, Dh Weinberg
The Effects Of Gasdynamics, Cooling, Star Formation, And Numerical Resolution In Simulations Of Cluster Formation, Gf Lewis, A Babul, N Katz, T Quinn, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We present the analysis of a suite of simulations of a Virgo-mass galaxy cluster. Undertaken within the framework of standard cold dark matter cosmology, these simulations were performed at differing resolutions and with increasingly complex physical processes, with the goal of identifying the effects of each on the evolution of the cluster. We focus on the cluster at the present epoch and examine properties including the radial distributions of density, temperature, entropy, and velocity. We also map "observable" projected properties such as the surface mass density, X-ray surface brightness, and Sunyaev-Zeldovich signature. We identify significant differences between the simulations, which …
Properties Of Galaxy Clusters: Mass And Correlation Functions, F Governato, A Babul, T Quinn, P Tozzi, Cm Baugh, N Katz, G Lake
Properties Of Galaxy Clusters: Mass And Correlation Functions, F Governato, A Babul, T Quinn, P Tozzi, Cm Baugh, N Katz, G Lake
Astronomy Department Faculty Publication Series
We analyse parallel N-body simulations of three cold dark matter (CDM) universes to study the abundance and clustering of galaxy clusters. The simulation boxes are 500 h−1 Mpc on a side and cover a volume comparable to that of the forthcoming Sloan Digital Sky Survey. The use of a treecode algorithm and 47 million particles allows us at the same time to achieve high mass and force resolution. We are thus able to make robust measurements of cluster properties with good number statistics up to a redshift larger than unity. We extract haloes using two independent, public domain …
The Clustering Of High-Redshift Galaxies In The Cold Dark Matter Scenario, N Katz, L Hernquist, Dh Weinberg
The Clustering Of High-Redshift Galaxies In The Cold Dark Matter Scenario, N Katz, L Hernquist, Dh Weinberg
Astronomy Department Faculty Publication Series
We investigate the clustering of high-redshift galaxies in five variants of the cold dark matter (CDM) scenario, using hydrodynamic cosmological simulations that resolve the formation of systems with circular velocities vc ≥ 100 km s-1 (Ω = 1) or vc ≥ 70 km s-1 (Ω = 0.4). Although the five models differ in their cosmological parameters and in the shapes and amplitudes of their mass power spectra, they predict remarkably similar galaxy clustering at z = 2, 3, and 4. The galaxy correlation functions show almost no evolution over this redshift range, even though the mass …