The bias of the submillimetre galaxy population: SMGs are poor tracers of the most massive structures in the z ~ 2 Universe

It is often claimed that overdensities of (or even individual bright) submillimetre-selected galaxies (SMGs) trace the assembly of the most-massive dark matter structures in the Universe. We test this claim by performing a counts-in-cells analysis of mock SMG catalogues derived from the Bolshoi cosmological simulation to investigate how well SMG associations trace the underlying dark matter structure. We find that SMGs exhibit a relatively complex bias: some regions of high SMG overdensity are underdense in terms of dark matter mass, and some regions of high dark matter overdensity contain no SMGs. Because of their rarity, Poisson noise causes scatter in the SMG overdensity at fixed dark matter overdensity. Consequently, rich associations of less-luminous, more-abundant galaxies (i.e. Lyman-break galaxy analogues) trace the highest dark matter overdensities much better than SMGs. Even on average, SMG associations are relatively poor tracers of the most significant dark matter overdensities because of 'downsizing': at z < ~2.5, the most-massive galaxies that reside in the highest dark matter overdensities have already had their star formation quenched and are thus no longer SMGs. At a given redshift, of the 10 per cent most-massive overdensities, only ~25 per cent contain at least one SMG, and less than a few per cent contain more than one SMG.Comment: 6 pages, 3 figures, 1 table; accepted for publication in MNRAS; minor revisions from previous version, conclusions unchange

A mass-dependent slope of the galaxy size-mass relation out to z ∼ 3 : further evidence for a direct relation between median galaxy size and median halo mass

We reassess the galaxy size-mass relation out to z similar to 3 using a new definition of size and a sample of >29,000 galaxies from the 3D-HST, CANDELS, and COSMOS-DASH surveys. Instead of the half-light radius r(50) we use r(80), the radius containing 80% of the stellar light. We find that the r(80)M(*) relation has the form of a broken power law, with a clear change of slope at a pivot mass M-p. Below the pivot mass the relation is shallow (r(80) proportional to M-*(0.)15); above it, it is steep (r(80) proportional to M-*(0.)6). The pivot mass increases with redshift, from log(M-p/M-circle dot) approximate to 10.2 at z = 0.4 to log(M-p/M-circle dot) approximate to 10.9 at z = 1.7-3. We compare these r(80)-M-* relations to the M-helo-M-* relations derived from galaxy-galaxy lensing, clustering analyses, and abundance matching techniques. Remarkably, the pivot stellar masses of both relations are consistent with each other at all redshifts, and the slopes are very similar both above and below the pivot when assuming M-halo proportional to r(8)(0)(3). The implied scaling factor to relate galaxy size to halo size is r(80)/R-vir = 0.047, independent of stellar mass and redshift. From redshift 0 to 1.5, the pivot mass also coincides with the mass where the fraction of star-forming galaxies is 50%, suggesting that the pivot mass reflects a transition from dissipational to dissipationless galaxy growth. Finally, our results imply that the scatter in the stellar-to-halo mass is relatively small for massive halos (similar to 0.2 dex for M-halo > 10(1)(2.)(5) M-circle dot)

A New View of the Size-Mass Distribution of Galaxies: Using r20r_{20} and r80r_{80} instead of r50r_{50}

When investigating the sizes of galaxies it is standard practice to use the half-light radius, $r_{50}$. Here we explore the effects of the size definition on the distribution of galaxies in the size -- stellar mass plane. Specifically, we consider $r_{20}$ and $r_{80}$, the radii that contain 20% and 80% of a galaxy's total luminosity, as determined from a Sersic profile fit, for galaxies in the 3D-HST/CANDELS and COSMOS-DASH surveys. These radii are calculated from size catalogs based on a simple calculation assuming a Sersic profile. We find that the size-mass distributions for $r_{20}$ and $r_{80}$ are markedly different from each other and also from the canonical $r_{50}$ distribution. The most striking difference is in the relative sizes of star forming and quiescent galaxies at fixed stellar mass. Whereas quiescent galaxies are smaller than star forming galaxies in $r_{50}$, this difference nearly vanishes for $r_{80}$. By contrast, the distance between the two populations increases for $r_{20}$. Considering all galaxies in a given stellar mass and redshift bin we detect a significant bimodality in the distribution of $r_{20}$, with one peak corresponding to star forming galaxies and the other to quiescent galaxies. We suggest that different measures of the size are tracing different physical processes within galaxies; $r_{20}$ is closely related to processes controlling the star formation rate of galaxies and $r_{80}$ may be sensitive to accretion processes and the relation of galaxies with their halos.Comment: Resubmitted to ApJL after responding to referee's comments. Please also see Mowla et al. submitted today as wel

Color gradients and half-mass radii of galaxies out to z=2z=2 in the CANDELS/3D-HST fields: further evidence for important differences in the evolution of mass-weighted and light-weighted sizes

Recent studies have indicated that the ratio between half-mass and half-light radii, $r_{\rm mass} / r_{\rm light}$, varies significantly as a function of stellar mass and redshift, complicating the interpretation of the ubiquitous $r_{\rm light}- M_*$ relation. To investigate, in this study we construct the light and color profiles of $\sim 3000$ galaxies at $1<z<2$ with $\log\, M_*/M_\odot > 10.25$ using $\texttt{imcascade}$, a Bayesian implementation of the Multi-Gaussian expansion (MGE) technique. $\texttt{imcascade}$ flexibly represents galaxy profiles using a series of Gaussians, free of any a-priori parameterization. We find that both star-forming and quiescent galaxies have on average negative color gradients. For star forming galaxies, we find steeper gradients that evolve with redshift and correlate with dust content. Using the color gradients as a proxy for gradients in the $M/L$ ratio we measure half mass radii for our sample of galaxies. There is significant scatter in individual $r_{\rm mass} / r_{\rm light}$ ratios, which is correlated with variation in the color gradients. We find that the median $r_{\rm mass} / r_{\rm light}$ ratio evolves from 0.75 at $z=2$ to 0.5 at $z=1$, consistent with previous results. We characterize the $r_{\rm mass}- M_*$ relation and we find that it has a shallower slope and shows less redshift evolution than the $r_{\rm light} - M_*$ relation. This applies both to star-forming and quiescent galaxies. We discuss some of the implications of using $r_{\rm mass}$ instead of $r_{\rm light}$, including an investigation of the size-inclination bias and a comparison to numerical simulations.Comment: Submitted to ApJ: Please find catalog of size and color gradient measurements here: https://raw.githubusercontent.com/tbmiller-astro/tbmiller-astro.github.io/main/assets/Miller2022_morph_CANDELs.tx

1-G Human Factors for Optimal Processing and Operability of Ground Systems up to CxP GOP PDR

During the mid stages of design development, up to Constellation Program (CxP) Preliminary Design Review (PDR), the requirements for leveraging I-G human factors for optimizing ground processing of Flight Hardware were mature for levels - 2, 3, 4, and 5. This paper gives an overview of the accomplishments achieved during that time. The main focus of this paper will be on the CxP Ground Operations Project human factors engineering analysis process using a Human Factors Engineering Analysis Tool (HFEAT) for developing the level- 5 requirements effecting the design development of the subsystems for Ground Support System (GSS), and Ground Support Equipment (GSE)

Investigating Overdensities around z > 6 Galaxies through ALMA Observations of [C II]

We present a search for companion [C II] emitters to known luminous sources at 6 < z < 6.5 in deep, archival ALMA observations. The observations are deep enough to detect sources with L_([CII])∼10⁸ at z ∼6. We identify three new robust line detections from a blind search of five deep fields centered on ultraluminous infrared galaxies and QSOs. We calculate the volume density of companions and find a relative overdensity of 6⁺⁴₋₃ and 86⁺⁶⁰₋₃₇ when comparing to current observational constraints and theoretical predictions, respectively. These results suggest that the central sources may be highly biased tracers of mass in the early universe. We find these companion lines to have comparable properties to other known galaxies at the same epoch. All companions lie less than 650 km s⁻¹ and between 25 and 60 kpc (projected) from their central source. To place these discoveries in context, we employ a mock galaxy catalog to estimate the luminosity function for [C II] during reionization and compare to our observations. The simulations support this result by showing a similar level of elevated counts found around such luminous [C II] sources

NMFS / Interagency Working Group Evaluation of CITES Criteria and Guidelines.

EXECUTIVE SUMMARY: At present, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) criteria used to assess whether a population qualifies for inclusion in the CITES Appendices relate to (A) size of the population, (B) area of distribution of the population, and (C) declines in the size of the population. Numeric guidelines are provided as indicators of a small population (less than 5,000 individuals), a small subpopulation (less than 500 individuals), a restricted area of distribution for a population (less than 10,000 km2), a restricted area of distribution for a subpopula-tion (less than 500 km2), a high rate of decline (a decrease of 50% or more in total within 5 years or two generations whichever is longer or, for a small wild population, a decline of 20% or more in total within ten years or three generations whichever is longer), large fluctuations (population size or area of distribution varies widely, rapidly and frequently, with a variation greater than one order of magnitude), and a short-term fluctuation (one of two years or less). The Working Group discussed several broad issues of relevance to the CITES criteria and guidelines. These included the importance of the historical extent of decline versus the recent rate of decline; the utility and validity of incorporating relative population productivity into decline criteria; the utility of absolute numbers for defining small populations or small areas; the appropriateness of generation times as time frames for examining declines; the importance of the magnitude and frequency of fluctuations as factors affecting risk of extinction; and the overall utility of numeric thresh-olds or guidelines