We combine data sets from the CGM2and CASBaH surveys to model a transition point,
The connection between galaxies and dark matter halos is often quantified using the stellar mass–halo mass (SMHM) relation. Optical and near-infrared imaging surveys have led to a broadly consistent picture of the evolving SMHM relation based on measurements of galaxy abundances and angular correlation functions. Spectroscopic surveys at
- NSF-PAR ID:
- 10485429
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 961
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 27
- Size(s):
- ["Article No. 27"]
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract R cross, between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies atz < 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01–20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover Hi Lyα . Our best-fitting model is a two-component model that combines a 3D absorber–galaxy cross-correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination ofR crossas a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with 108≤M ⋆/M ⊙≤ 1010.5, we find thatR cross(M ⋆) ≈ 2.0 ± 0.6R vir. Additionally, we find excellent agreement betweenR cross(M ⋆) and the theoretically determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution atz < 0.5 that distributeT ≈ 104K gas to distances beyond the virial radius. -
more » « less
Abstract The abundance of cold molecular gas plays a crucial role in models of galaxy evolution. While deep spectroscopic surveys of CO emission lines have been a primary tool for measuring this abundance, the difficulty of these observations has motivated alternative approaches to studying molecular gas content. One technique, line intensity mapping, seeks to constrain the average molecular gas properties of large samples of individually undetectable galaxies through the CO brightness power spectrum. Here we present constraints on the cross-power spectrum between CO intensity maps and optical galaxy catalogs. This cross-measurement allows us to check for systematic problems in CO intensity mapping data, and validate the data analysis used for the auto-power spectrum measurement of the CO Power Spectrum Survey. We place a 2
σ upper limit on the band-averaged CO-galaxy cross-power ofP ×< 540μ K h−3Mpc3. Our measurement favors a nonzero 〈T CO〉 at around 90% confidence and gives an upper limit on the mean molecular gas density atz ∼ 2.6 of 7.7 × 108M ⊙Mpc−3. We forecast the expected cross-power spectrum by applying a number of literature prescriptions for the CO luminosity–halo mass relation to a suite of mock light cones. Under the most optimistic forecasts, the cross-spectrum could be detected with only moderate extensions of the data used here, while more conservative models could be detected with a factor of 10 increase in sensitivity. Ongoing CO intensity mapping experiments will target fields allowing for extensive cross-correlation analysis and should reach the sensitivity required to detect the cross-spectrum signal. -
more » « less
Abstract We present measurements of black hole masses and Eddington ratios (
λ Edd) for a sample of 38 bright (M 1450< −24.4 mag) quasars at 5.8 ≲z ≲ 7.5, derived from Very Large Telescope/X–shooter near–IR spectroscopy of their broad Civ and Mgii emission lines. The black hole masses (on average,M BH∼ 4.6 × 109M ⊙) and accretion rates (0.1 ≲λ Edd≲ 1.0) are broadly consistent with that of similarly luminous 0.3 ≲z ≲ 2.3 quasars, but there is evidence for a mild increase in the Eddington ratio abovez ≳ 6. Combined with deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [CII ] 158μ m line from the host galaxies and VLT/MUSE investigations of the extended Lyα halos, this study provides fundamental clues to models of the formation and growth of the first massive galaxies and black holes. Compared to local scaling relations,z ≳ 5.7 black holes appear to be over-massive relative to their hosts, with accretion properties that do not change with host galaxy morphologies. Assuming that the kinematics of theT ∼ 104K gas, traced by the extended Lyα halos, are dominated by the gravitational potential of the dark matter halo, we observe a similar relation between black hole mass and circular velocity as reported forz ∼ 0 galaxies. These results paint a picture where the first supermassive black holes reside in massive halos atz ≳ 6 and lead the first stages of galaxy formation by rapidly growing in mass with a duty cycle of order unity. The duty cycle needs to drastically drop toward lower redshifts, while the host galaxies continue forming stars at a rate of hundreds of solar masses per year, sustained by the large reservoirs of cool gas surrounding them. -
more » « less
Abstract We present the stellar mass–stellar metallicity relation for 3491 star-forming galaxies at 2 ≲
z ≲ 3 using rest-frame far-ultraviolet spectra from the Lyα Tomography IMACS Survey (LATIS). We fit stellar population synthesis models from the Binary Population And Spectral Synthesis code (v2.2.1) to medium-resolution (R ∼ 1000) and high signal-to-noise (>30 per 100 km s−1over the wavelength range 1221–1800 Å) composite spectra of galaxies in bins of stellar mass to determine their stellar metallicity, primarily tracing Fe/H. We find a strong correlation between stellar mass and stellar metallicity, with stellar metallicity monotonically increasing with stellar mass at low masses and flattening at high masses (M *≳ 1010.3M ⊙). Additionally, we compare our stellar metallicity measurements with the gas-phase oxygen abundance of galaxies at similar redshift and estimate the average [α /Fe] ∼ 0.6. Such highα -enhancement indicates that high-redshift galaxies have not yet undergone significant iron enrichment through Type Ia supernovae. Moreover, we utilize an analytic chemical evolution model to constrain the mass loading parameter of galactic winds as a function of stellar mass. We find that as the stellar mass increases, the mass loading parameter decreases. The parameter then flattens or reaches a turning point at aroundM *∼ 1010.5M ⊙. Our findings may signal the onset of black-hole-driven outflows atz ∼ 2.5 for galaxies withM *≳ 1010.5M ⊙. -
more » « less
Abstract It has been well established in the local universe that galaxy properties differ based on the large-scale environment in which they reside. As luminous Ly
α nebulae have been shown to trace overdense environments atz ∼ 2–3, comparing the properties of galaxies within Lyα nebulae systems to those in the field can provide insight into how and when locally observed trends between galaxy properties and environment emerged. Six Lyα nebulae were discovered atz ∼ 2.3 in a blind search of the GOODS-S extragalactic field, a region also covered by the 3D-HST spectroscopic survey. Utilizing 3D-HST data, we identified 86 galaxies in the vicinity of these nebulae and used statistical tests to compare their physical properties to galaxies elsewhere in the field. Galaxies lying within 320 proper kpc of a Lyα nebula are roughly half a magnitude brighter than those in the field, with higher stellar masses, higher star formation rates, and larger effective radii. Even when considering the effects of sample incompleteness, our study suggests that galaxies in overdensities atz ∼ 2.3 traced by Lyα nebulae are being influenced by their environment. Furthermore, Lyα -nebula-associated galaxies lie on the same main sequence of star formation as field galaxies but have a larger proportion of high-mass galaxies, consistent with the idea that galaxy evolution is accelerated in rich environments. Expanded surveys for Lyα nebulae in other deep extragalactic fields and galaxy spectroscopic follow-up with the James Webb Space Telescope (JWST) will better constrain the demographics of Lyα -nebula-associated galaxies.
