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Register a new userThe Galaxy-Halo Connection for $1.5lesssim zlesssim5$ as revealed by the emph{Spitzer} Matching survey of the UltraVISTA ultra-deep Stripes
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William Cowley
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The emph{Spitzer} Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) provides unparalleled depth at $3.6$ and $4.5$~$mu$m over $sim0.66$~deg$^2$ of the COSMOS field, allowing precise photometric determinations of redshift and stellar mass. From this unique dataset we can connect galaxy samples, selected by stellar mass, to their host dark matter halos for $1.5<z<5.0$, filling in a large hitherto unexplored region of the parameter space. To interpret the observed galaxy clustering we utilize a phenomenological halo model, combined with a novel method to account for uncertainties arising from the use of photometric redshifts. We find that the satellite fraction decreases with increasing redshift and that the clustering amplitude (e.g., comoving correlation length / large-scale bias) displays monotonic trends with redshift and stellar mass. Applying $Lambda$CDM halo mass accretion histories and cumulative abundance arguments for the evolution of stellar mass content we propose pathways for the coevolution of dark matter and stellar mass assembly. Additionally, we are able to estimate that the halo mass at which the ratio of stellar to halo mass is maximized is $10^{12.5_{-0.08}^{+0.10}}$~M$_{odot}$ at $zsim2.5$. This peak halo mass is here inferred for the first time from stellar mass-selected clustering measurements at $zgtrsim2$, and implies mild evolution of this quantity for $zlesssim3$, consistent with constraints from abundance-matching techniques.
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The Spitzer Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS) has obtained the largest ultra-deep Spitzer maps to date in a single field of the sky. We considered the sample of about 66,000 SMUVS sources at $z=2-6$ to investigate the evolution of dusty and non-dusty galaxies with stellar mass through the analysis of the galaxy stellar mass function (GSMF). We further divide our non-dusty galaxy sample with rest-frame optical colours to isolate red quiescent (`passive) galaxies. At each redshift, we identify a characteristic stellar mass in the GSMF above which dusty galaxies dominate, or are at least as important as non-dusty galaxies. Below that stellar mass, non-dusty galaxies comprise about 80% of all sources, at all redshifts except at $z=4-5$. The percentage of dusty galaxies at $z=4-5$ is unusually high: 30-40% for $M_{*}=10^9 - 10^{10.5} , rm M_odot$ and $>80%$ at $M_*>10^{11} , rm M_odot$, which indicates that dust obscuration is of major importance in this cosmic period. The overall percentage of massive ($log_{10} (M_*/M_odot)>10.6$) galaxies that are quiescent increases with decreasing redshift, reaching $>30%$ at $zsim2$. Instead, the quiescent percentage among intermediate-mass galaxies (with $log_{10} (M_*/M_odot)=9.7-10.6$) stays roughly constant at a $sim 10%$ level. Our results indicate that massive and intermediate-mass galaxies clearly have different evolutionary paths in the young Universe, and are consistent with the scenario of galaxy downsizing.
In recent years, massive new spectroscopic data sets, such as the over half million stellar spectra obtained during the course of SDSS (in particular its sub-survey SEGUE), have provided the quantitative detail required to formulate a coherent story of the assembly and evolution of the Milky Way. The disk and halo systems of our Galaxy have been shown to be both more complex, and more interesting, than previously thought. Here we concentrate on the halo system of the Milky Way. New data from SDSS/SEGUE has revealed that the halo system comprises at least two components, the inner halo and the outer halo, with demonstrably different characteristics (metallicity distributions, density distributions, kinematics, etc.). In addition to suggesting new ways to examine these data, the inner/outer halo dichotomy has enabled an understanding of at least one long-standing observational result, the increase of the fraction of carbon-enhanced metal-poor (CEMP) stars with decreasing metallicity.
We present a series of results from a clustering analysis of the first data release of the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey. VIDEO is the only survey currently capable of probing the bulk of stellar mass in galaxies at redshifts corresponding to the peak of star formation on degree scales. Galaxy clustering is measured with the two-point correlation function, which is calculated using a non parametric kernel based density estimator. We use our measurements to investigate the connection between the galaxies and the host dark matter halo using a halo occupation distribution methodology, deriving bias, satellite fractions, and typical host halo masses for stellar masses between $10^{9.35}M_{odot}$ and $10^{10.85}M_{odot}$, at redshifts $0.5<z<1.7$. Our results show typical halo mass increasing with stellar mass (with moderate scatter) and bias increasing with stellar mass and redshift consistent with previous studies. We find the satellite fraction increased towards low redshifts, increasing from $sim 5%$ at $zsim 1.5$, to $sim 20%$ at $zsim 0.6$, also increasing for lower mass galaxies. We combine our results to derive the stellar mass to halo mass ratio for both satellites and centrals over a range of halo masses and find the peak corresponding to the halo mass with maximum star formation efficiency to be $ sim 2 times10^{12} M_{odot}$ over cosmic time, finding no evidence for evolution.
This paper seeks to test if the large-scale galaxy distribution can be characterized as a fractal system. Tools appropriate for describing galaxy fractal structures with a single fractal dimension $D$ in relativistic settings are developed and applied to the UltraVISTA galaxy survey. A graph of volume-limited samples corresponding to the redshift limits in each redshift bins for absolute magnitude is presented. Fractal analysis using the standard $Lambda$CDM cosmological model is applied to a reduced subsample in the range $0.1le z le 4$, and the entire sample within $0.1le zle 6$. Three relativistic distances are used, the luminosity distance $d_L$, redshift distance $d_z$ and galaxy area distance $d_G$, because for data at $zgtrsim 0.3$ relativistic effects are such that for the same $z$ these distance definitions yield different values. The results show two consecutive and distinct redshift ranges in both the reduced and complete samples where the data behave as a single fractal galaxy structure. For the reduced subsample we found that the fractal dimension is $D=left(1.58pm0.20right)$ for $z<1$, and $D=left(0.59pm0.28right)$ for $1le zle 4$. The complete sample yielded $D=left(1.63pm0.20right)$ for $z<1$ and $D=left(0.52pm0.29right)$ for $1le zle6$. These results are consistent with those found by Conde-Saavedra et al. (2015; arXiv:1409.5409v1), where a similar analysis was applied to a much more limited survey at equivalent redshift depths, and suggest that either there are yet unclear observational biases causing such decrease in the fractal dimension, or the galaxy clustering was possibly more sparse and the universe void dominated in a not too distant past.
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