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We investigate the stellar populations for a sample of 161 massive, mainly quiescent galaxies at 〈z obs〉 = 0.8 with deep Keck/DEIMOS rest-frame optical spectroscopy (HALO7D survey). With the fully Bayesian framework Prospector, we simultaneously fit the spectroscopic and photometric data with an advanced physical model (including nonparametric star formation histories, emission lines, variable dust attenuation law, and dust and active galactic nucleus emission), together with an uncertainty and outlier model. We show that both spectroscopy and photometry are needed to break the dust–age–metallicity degeneracy. We find a large diversity of star formation histories: although the most massive (M ⋆ > 2 × 1011 M ⊙) galaxies formed the earliest (formation redshift of z f ≈ 5–10 with a short star formation timescale of τ SF ≲ 1 Gyr), lower-mass galaxies have a wide range of formation redshifts, leading to only a weak trend of z f with M ⋆. Interestingly, several low-mass galaxies have formation redshifts of z f ≈ 5–8. Star-forming galaxies evolve about the star-forming main sequence, crossing the ridgeline several times in their past. Quiescent galaxies show a wide range and continuous distribution of quenching timescales (τ quench ≈ 0–5 Gyr) with a median of 〈τquench〉=1.0−0.9+0.8Gyr and of quenching epochs of z quench ≈ 0.8–5.0 ( 〈zquench〉=1.3−0.4+0.7 ). This large diversity of quenching timescales and epochs points toward a combination of internal and external quenching mechanisms. In our sample, rejuvenation and “late bloomers” are uncommon. In summary, our analysis supports the “grow-and-quench” framework and is consistent with a wide and continuously populated diversity of quenching timescales.

We investigate how cosmic web structures affect galaxy quenching in the IllustrisTNG (TNG100) cosmological simulations by reconstructing the cosmic web within each snapshot using the DisPerSE framework. We measure the comoving distance from each galaxy with stellar mass log(M*/M⊙)≥8 to the nearest node (d node) and the nearest filament spine (d fil) to study the dependence of both the median specific star formation rate (〈sSFR〉) and the median gas fraction (〈f gas〉) on these distances. We find that the 〈sSFR〉 of galaxies is only dependent on the cosmic web environment at z < 2, with the dependence increasing with time. At z ≤ 0.5, 8≤log(M*/M⊙)<9 galaxies are quenched at d node ≲ 1 Mpc, and have significantly suppressed star formation at d fil ≲ 1 Mpc, trends driven mostly by satellite galaxies. At z ≤ 1, in contrast to the monotonic drop in 〈sSFR〉 of log(M*/M⊙)<10 galaxies with decreasing d node and d fil, log(M*/M⊙)≥10 galaxies—both centrals and satellites—experience an upturn in 〈sSFR〉 at d node ≲ 0.2 Mpc. Much of this cosmic web dependence of star formation activity can be explained by an evolution in 〈f gas〉. Our results suggest that in the past ∼10 Gyr, low-mass satellites are quenched by rapid gas stripping in dense environments near nodes and gradual gas starvation in intermediate-density environments near filaments. At earlier times, cosmic web structures efficiently channeled cold gas into most galaxies. State-of-the-art ongoing spectroscopic surveys such as the Sloan Digital Sky Survey and DESI, as well as those planned with the Subaru Prime Focus Spectrograph, JWST, and Roman, are required to test our predictions against observations.

The specific star formation rate (sSFR) is commonly used to describe the level of galaxy star formation (SF) and to select quenched galaxies. However, since it is a relative measure of the young-to-old population, an ambiguity in its interpretation may arise because a low sSFR can be due to either a substantial previous mass buildup or SF activity that is low. We show, using large samples spanning 0 < z < 2, that the normalization of the star formation rate (SFR) by the physical extent over which SF is taking place (i.e., the SFR surface density, ΣSFR) overcomes this ambiguity. ΣSFR has a strong physical basis, being tied to the molecular gas density and the effectiveness of stellar feedback, so we propose ΣSFR–M * as an important galaxy evolution diagram to complement (s)SFR–M * diagrams. Using the ΣSFR–M * diagram we confirm the Schiminovich et al. result that the level of SF along the main sequence today is only weakly mass-dependent—high-mass galaxies, despite their redder colors, are as active as blue, low-mass ones. At higher redshift, the slope of the “ΣSFR main sequence” steepens, signaling the epoch of bulge buildup in massive galaxies. We also find that ΣSFR based on the optical isophotal radius more cleanly selects both starbursting and spheroid-dominated (early-type) galaxies than the sSFR. One implication of our analysis is that the assessment of the inside-out versus outside-in quenching scenarios should consider both sSFR and ΣSFR radial profiles, because ample SF may be present in bulges with low sSFRs (red color).

We present a novel approach for identifying cosmic web filaments within the DisPerSE structure identification framework, using cosmic density field estimates from the Monte Carlo Physarum Machine (MCPM), inspired by the slime mold organism. We apply our method to the IllustrisTNG (TNG100) cosmological simulations and investigate the impact of filaments on galaxies. The MCPM density field is superior to the Delaunay tessellation field estimator in tracing the true underlying matter distribution and allows filaments to be identified with higher fidelity, finding more low-prominence/diffuse filaments. Using our new filament catalogs, we find that ≳90% of galaxies are located within ∼1.5 Mpc of a filamentary spine, with little change in the median star formation activity with distance to the nearest filament. Instead, we uncover a differential effect of the local filament line density, Σfil (MCPM)—the total MCPM overdensity per unit length along a filament segment—on galaxy formation: most galaxies are quenched and gas-poor near high-line density filaments at z ≤ 1. At earlier times, the filamentary environment appears to have no effect on galactic gas supply and quenching. At z = 0, quenching in log(M*/M⊙)≳10.5 galaxies is mainly driven by mass, while lower-mass galaxies are significantly affected by the filament line density. Satellites are far more susceptible to filaments than centrals. The local environments of massive halos are not sufficient to account for the effect of filament line density on gas removal and quenching. Our new approach holds great promise for observationally identifying filaments from galaxy surveys such as SDSS and DESI.

Galaxies and black holes The massive black holes found at the centre of most galaxies, including our own, release prodigious amounts of energy that power spectacular phenomena such as quasars and active galactic nuclei. If just a tiny fraction of that energy were absorbed into the host galaxy it could stop star formation in its tracks by heating and ejecting the ambient gas. The latest of our 'IYA 2009' reviews, marking the International Year of Astronomy and collected together on http://www.nature.com/astro09 , tackles one of the central questions in galaxy evolution — the degree to which black hole activity has limited star formation in large elliptical galaxies. These contain much less cool gas and fewer young stars than spiral galaxies, a contrast that could relate to how the central black hole interacts with its surroundings. Virtually all massive galaxies host central black holes, the growth of which releases vast amounts of energy that powers quasars and other weaker active galactic nuclei. However, a tiny fraction of this energy could halt star formation by heating and ejecting ambient gas; a central question in galaxy evolution is the degree to which this process has caused the decline of star formation in large elliptical galaxies. Virtually all massive galaxies, including our own, host central black holes ranging in mass from millions to billions of solar masses. The growth of these black holes releases vast amounts of energy that powers quasars and other weaker active galactic nuclei. A tiny fraction of this energy, if absorbed by the host galaxy, could halt star formation by heating and ejecting ambient gas. A central question in galaxy evolution is the degree to which this process has caused the decline of star formation in large elliptical galaxies, which typically have little cold gas and few young stars, unlike spiral galaxies.

In this work, we use ∼500 low-redshift (z ∼ 0.1) X-ray active galactic nuclei (AGNs) observed by XMM-Newton and the Sloan Digital Sky Survey (SDSS) to investigate the prevalence and nature of AGNs that apparently lack optical emission lines (“optically dull AGNs”). Although one quarter of spectra appear absorption-line dominated in visual assessment, line extraction with robust continuum subtraction from the MPA/JHU catalog reveals usable [O iii] measurements in 98% of the sample, allowing us to study [O iii]-underluminous AGNs together with more typical AGNs in the context of the L [O III]–L X relation. We find that “optically dull AGNs” do not constitute a distinct population of AGNs. Instead, they are the [O iii]-underluminous tail of a single, unimodal L [O III]–L X relation that has substantial scatter (0.6 dex). We find the degree to which an AGN is underluminous in [O iii] correlates with the specific star formation rate or D 4000 index of the host, which are both linked to the molecular gas fraction. Thus the emerging physical picture for the large scatter seems to involve the gas content of the narrow-line region. We find no significant role for previously proposed scenarios for the presence of optically dull AGNs, such as host dilution or dust obscuration. Despite occasionally weak lines in SDSS spectra, >80% of X-ray AGNs are identified as such with the Baldwin–Phillips–Terlevich diagram. More than 90% are classified as AGNs based only on [N ii]/Hα, providing more complete AGN samples when [O iii] or Hβ are weak. X-ray AGNs with LINER spectra obey essentially the same L [O III]–L X relation as Seyfert 2s, suggesting their line emission is produced by AGN activity.

Strong galactic winds are ubiquitous at z ≳ 1. However, it is not well-known where inside galaxies these winds are launched from. We study the cool winds (∼104 K) in two spatial regions of a massive galaxy at z = 1.3, which we nickname the “Baltimore Oriole’s Nest.” The galaxy has a stellar mass of 1010.3±0.3 M ⊙, is located on the star-forming main sequence, and has a morphology indicative of a recent merger. Gas kinematics indicate a dynamically complex system with velocity gradients ranging from 0 to 60 km s−1. The two regions studied are: a dust-reddened center (Central region), and a blue arc at 7 kpc from the center (Arc region). We measure the Fe ii and Mg ii absorption line profiles from deep Keck/DEIMOS spectra. Blueshifted wings up to 450 km s−1 are found for both regions. The Fe ii column densities of winds are 1014.7±0.2 cm−2 and 1014.6±0.2 cm−2 toward the Central and Arc regions, respectively. Our measurements suggest that the winds are most likely launched from both regions. The winds may be driven by the spatially extended star formation, the surface density of which is around 0.2 M ⊙ yr−1 · kpc−2 in both regions. The mass outflow rates are estimated to be 4 M ⊙ yr−1 and 3 M ⊙ yr−1 for the Central and Arc regions, with uncertainties of one order of magnitude or more. The findings of this work and a few previous studies suggest that the cool galactic winds at z ≳ 1 might be commonly launched from the entire spatial extents of their host galaxies, due to extended galaxy star formation.

Many universities acknowledge a responsibility to address climate change and are actively working to meet this goal in academic programs and undergraduate curricula. This paper provides insights from interviews with university leaders from 20 American and Canadian institutions pursuing climate action via education. Interviewees described a range of initiatives, including new General Education requirements (GEs), cross-disciplinary courses, domain-specific classes, and certificate programs, as well as the establishment of dedicated climate schools. Pathways for curricular change include academic senate climate committees, top-down support from university leadership, bottom-up advocacy and activism from faculty and students, and opportunities to leverage evolving systems. To increase climate-teaching capacity, interviewees reported instituting team teaching, supporting faculty learning opportunities, hiring faculty with climate expertise, and partnering with organizations outside academia. Qualitative data collected during these interviews were thematically coded, revealing significant takeaways including the need to appropriately reward faculty for climate-teaching efforts and to recognize the complementary virtues of high-level courses like GEs with broad reach versus deeper dives for climate-related majors with targeted reach. This paper synthesizes advice from educators who succeeded in increasing climate education at their institutions and concludes with suggestions on how to integrate climate more fully into academia’s educational mission.

We present a catalog of spectroscopically measured redshifts over 0 < z < 2 and emission-line fluxes for 1440 galaxies. The majority (∼65%) of the galaxies come from the HALO7D survey, with the remainder from the DEEPwinds program. This catalog includes redshifts for 646 dwarf galaxies with log(M⋆/M⊙)<9.5 . Eight-hundred and ten catalog galaxies did not have previously published spectroscopic redshifts, including 454 dwarf galaxies. HALO7D used the DEIMOS spectrograph on the Keck II telescope to take very deep (up to 32 hr exposure, with a median of ∼7 hr) optical spectroscopy in the COSMOS, EGS, GOODS-North, and GOODS-South CANDELS fields, and in some areas outside CANDELS. We compare our redshift results to existing spectroscopic and photometric redshifts in these fields, finding only a 1% rate of discrepancy with other spectroscopic redshifts. We measure a small increase in median photometric redshift error (from 1.0% to 1.3%) and catastrophic outlier rate (from 3.5% to 8%) with decreasing stellar mass. We obtained successful redshift fits for 75% of massive galaxies, and demonstrate a similar 70%–75% successful redshift measurement rate in 8.5

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