First Results from SMAUG: Insights into Star Formation Conditions from Spatially Resolved ISM Properties in TNG50
Abstract Physical and chemical properties of the interstellar medium (ISM) at subgalactic (∼kiloparsec) scales play an indispensable role in controlling the ability of gas to form stars. In this paper, we use the TNG50 cosmological simulation to explore the physical parameter space of eight resolved ISM properties in star-forming regions to constrain the areas of this hyperspace where most star-forming environments exist. We deconstruct our simulated galaxies spanning a wide range of mass ( M ⋆ = 10 7 –10 11 M ⊙ ) and redshift (0 ≤ z ≤ 3) into kiloparsec-sized regions and statistically analyze the gas/stellar surface densities, gas metallicity, vertical stellar velocity dispersion, epicyclic frequency, and dark-matter volumetric density representative of each region in the context of their star formation activity and environment (radial galactocentric location). By examining the star formation rate (SFR) weighted distributions of these properties, we show that stars primarily form in two distinct environmental regimes, which are brought about by an underlying bicomponent radial SFR profile in galaxies. We examine how the relative prominence of these regimes depends on galaxy mass and cosmic time. We also compare our findings with those from integral field spectroscopy observations and find similarities as well as more »
Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Award ID(s):
Publication Date:
NSF-PAR ID:
10347980
Journal Name:
The Astrophysical Journal
Volume:
926
Issue:
2
Page Range or eLocation-ID:
139
ISSN:
0004-637X
National Science Foundation
##### More Like this
1. Abstract We report Hubble Space Telescope Cosmic Origins Spectrograph spectroscopy of 10 quasars with foreground star-forming galaxies at 0.02 < z < 0.14 within impact parameters of ∼1–7 kpc. We detect damped/sub-damped Ly α (DLA/sub-DLA) absorption in 100% of cases where no higher-redshift Lyman-limit systems extinguish the flux at the expected wavelength of Ly α absorption, obtaining the largest targeted sample of DLA/sub-DLAs in low-redshift galaxies. We present absorption measurements of neutral hydrogen and metals. Additionally, we present Green Bank Telescope 21 cm emission measurements for five of the galaxies (including two detections). Combining our sample with the literature, we construct a sample of 117 galaxies associated with DLA/sub-DLAs spanning 0 < z < 4.4, and examine trends between gas and stellar properties, and with redshift. The H i column density is anticorrelated with impact parameter and stellar mass. More massive galaxies appear to have gas-rich regions out to larger distances. The specific star formation rate (sSFR) of absorbing galaxies increases with redshift and decreases with M *, consistent with evolution of the star formation main sequence (SFMS). However, ∼20% of absorbing galaxies lie below the SFMS, indicating that some DLA/sub-DLAs trace galaxies with longer-than-typical gas-depletion timescales. Most DLA/sub-DLA galaxiesmore »
2. Abstract Nuclear rings are excellent laboratories for studying intense star formation. We present results from a study of nuclear star-forming rings in five nearby normal galaxies from the Star Formation in Radio Survey (SFRS) and four local LIRGs from the Great Observatories All-sky LIRG Survey at sub-kiloparsec resolutions using Very Large Array high-frequency radio continuum observations. We find that nuclear ring star formation (NRSF) contributes 49%–60% of the total star formation of the LIRGs, compared to 7%–40% for the normal galaxies. We characterize a total of 57 individual star-forming regions in these rings, and find that with measured sizes of 10–200 pc, NRSF regions in the LIRGs have star formation rate (SFR) and Σ SFR up to 1.7 M ⊙ yr −1 and 402 M ⊙ yr −1 kpc −2 , respectively, which are about 10 times higher than in NRSF regions in the normal galaxies with similar sizes, and comparable to lensed high- z star-forming regions. At ∼100–300 pc scales, we estimate low contributions (<50%) of thermal free–free emission to total radio continuum emission at 33 GHz in the NRSF regions in the LIRGs, but large variations possibly exist at smaller physical scales. Finally, using archival sub-kiloparsec resolution COmore »
3. Abstract We report the first spatially resolved measurements of gas-phase metallicity radial gradients in star-forming galaxies in overdense environments at z ≳ 2. The spectroscopic data are acquired by the MAMMOTH-Grism survey, a Hubble Space Telescope (HST) cycle 28 medium program. This program is obtaining 45 orbits of WFC3/IR grism spectroscopy in the density peak regions of three massive galaxy protoclusters (BOSS 1244, BOSS 1542, and BOSS 1441) at z = 2–3. Our sample in the BOSS 1244 field consists of 20 galaxies with stellar mass ranging from 10 9.0 to 10 10.3 M ⊙ , star formation rate (SFR) from 10 to 240 M ⊙ yr −1 , and global gas-phase metallicity ( 12 + log ( O / H ) ) from 8.2 to 8.6. At 1 σ confidence level, 2/20 galaxies in our sample show positive (inverted) gradients—the relative abundance of oxygen increasing with galactocentric radius, opposite the usual trend. Furthermore, 1/20 shows negative gradients, and 17/20 are consistent with flat gradients. This high fraction of flat/inverted gradients is uncommon in simulations and previous observations conducted in blank fields at similar redshifts. To understand this, we investigate the correlations among various observed properties of our sample galaxies.more »
4. ABSTRACT

We use the simba cosmological galaxy formation simulation to investigate the relationship between major mergers ($\lesssim$4:1), starbursts, and galaxy quenching. Mergers are identified via sudden jumps in stellar mass M* well above that expected from in situ star formation, while quenching is defined as going from specific star formation rate (sSFR) $\gt t_{\rm H}^{-1}$ to $\lt 0.2t_{\rm H}^{-1}$, where tH is the Hubble time. At z ≈ 0–3, mergers show ∼2–3× higher SFR than a mass-matched sample of star-forming galaxies, but globally represent $\lesssim 1{{\ \rm per\ cent}}$ of the cosmic SF budget. At low masses, the increase in SFR in mergers is mostly attributed to an increase in the H2 content, but for $M_*\gtrsim 10^{10.5} \,\mathrm{ M}_{\odot }$ mergers also show an elevated star formation efficiency suggesting denser gas within merging galaxies. The merger rate for star-forming galaxies shows a rapid increase with redshift, ∝(1 + z)3.5, but the quenching rate evolves much more slowly, ∝(1 + z)0.9; there are insufficient mergers to explain the quenching rate at $z\lesssim 1.5$. simba first quenches galaxies at $z\gtrsim 3$, with a number density in good agreement with observations. The quenching time-scales τq are strongly bimodal, with ‘slow’ quenchings (τq ∼ 0.1tH) dominating overall,more »

5. ABSTRACT We investigate the spatial structure and evolution of star formation and the interstellar medium (ISM) in interacting galaxies. We use an extensive suite of parsec-scale galaxy-merger simulations (stellar mass ratio = 2.5:1), which employs the ‘Feedback In Realistic Environments-2’ model (fire-2). This framework resolves star formation, feedback processes, and the multiphase structure of the ISM. We focus on the galaxy-pair stages of interaction. We find that close encounters substantially augment cool (H i) and cold-dense (H2) gas budgets, elevating the formation of new stars as a result. This enhancement is centrally concentrated for the secondary galaxy, and more radially extended for the primary. This behaviour is weakly dependent on orbital geometry. We also find that galaxies with elevated global star formation rate (SFR) experience intense nuclear SFR enhancement, driven by high levels of either star formation efficiency (SFE) or available cold-dense gas fuel. Galaxies with suppressed global SFR also contain a nuclear cold-dense gas reservoir, but low SFE levels diminish SFR in the central region. Concretely, in the majority of cases, SFR enhancement in the central kiloparsec is fuel-driven (55 per cent for the secondary, 71 per cent for the primary) – while central SFR suppression is efficiency-driven (91 per cent for the secondary, 97 per cent formore »