Charlie Conroy

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The stellar initial mass function (IMF) describes the mass distribution of stars at the time of their formation and is of fundamental importance for many areas of astrophysics. The IMF is reasonably well constrained in the disk of the Milky Way but we have very little direct information on the form of the IMF in other galaxies and at earlier cosmic epochs.(More)
We conduct a comprehensive analysis of the relationship between central galaxies and their host dark matter halos, as characterized by the stellar mass – halo mass (SM–HM) relation, with rigorous consideration of uncertainties. Our analysis focuses on results from the abundance matching technique, which assumes that every dark matter halo or subhalo above a(More)
A simple, observationally-motivated model is presented for understanding how halo masses, galaxy stellar masses, and star formation rates are related, and how these relations evolve with time. The relation between halo mass and galaxy stellar mass is determined by matching the observed spatial abundance of galaxies to the expected spatial abundance of halos(More)
We use a set of simulation-based models for the dissipationless evolution of galaxies since z = 1 to constrain the fate of accreted satellites embedded in dark matter subhalos. These models assign stellar mass to dark matter halos at z = 1 by relating the observed galaxy stellar mass function (GSMF) to the halo+subhalo mass function monotonically. The(More)
We employ high-resolution dissipationless simulations of the concordance ΛCDM cosmology (Ω0 = 1 − ΩΛ = 0.3, h = 0.7, σ8 = 0.9) to model the observed luminosity dependence and evolution of galaxy clustering through most of the age of the universe, from z ∼ 5 to z ∼ 0. We use a simple, nonparametric model which monotonically relates galaxy luminosities to the(More)
We present measurements of the void probability function (VPF) at z ∼ 1 using data from the DEEP2 Redshift Survey and its evolution to z ∼ 0 using data from the Sloan Digital Sky Survey (SDSS). We measure the VPF as a function of galaxy color and luminosity in both surveys and find that it mimics trends displayed in the two-point correlation function, ξ;(More)
We measure the evolution in the virial mass-to-light ratio (M200/LB) and virial-to-stellar mass ratio (M200/M∗) for isolated ∼ L galaxies between z ∼ 1 and z ∼ 0 by combining data from the DEEP2 Galaxy Redshift Survey and the Sloan Digital Sky Survey. Utilizing the motions of satellite galaxies around isolated galaxies, we measure line-of-sight velocity(More)
In the ΛCDM cosmology dark matter halos grow primarily through the accretion of smaller halos. Much of the mass in a halo of 10 M⊙ comes in through accretion of ∼ 10 M⊙ halos. If each such halo hosted one luminous red galaxy (LRG) then the accretion of so many halos is at odds with the observed number of LRGs in clusters unless these accreted LRGs merge or(More)
Large dust grains can fluctuate dramatically in their local density, relative to the gas, in neutral, turbulent disks. Small, high-redshift galaxies (before reionization) represent ideal environments for this process. We show via simple arguments and simulations that order-of-magnitude fluctuations are expected in local abundances of large grains (> 100Å)(More)
A novel technique is employed for estimating attenuation curves in galaxies where only photometry and spectroscopic redshifts are available. This technique provides a powerful measure of particular extinction features such as the UV bump at 2175Å, which has been observed in environments ranging from the Milky Way to high–redshift star–forming galaxies.(More)