Quiescent Galaxies Research Articles

To High Redshift and Low Mass: Exploring the Emergence of Quenched Galaxies and Their Environments at 3 < z < 6 in the Ultra-deep JADES MIRI F770W Parallel

We present the robust selection of high-redshift quiescent galaxies (QG) and poststarburst (PSB) galaxies using ultra-deep NIRCam and MIRI imaging from the JWST Advanced Deep Extragalactic Survey (JADES). At 3 < z < 6, MIRI 7.7 μm imaging provides rest-frame J band, which is commonly used to break the degeneracy between old stellar populations and dust attenuation at lower redshifts. We identify 23 passively evolving galaxies in UVJ color space in a mass-limited (log M ⋆/M ⊙ ≥ 8.5) sample over 8.8 arcmin2. An evaluation of the contribution of the 7.7 μm shows that JADES-like NIRCam coverage (9+ photometric bands) can compensate for lacking the J band at these redshifts; however, more limited three-band selections perform better with MIRI. Our sample is characterized by rapid quenching timescales (∼100–600 Myr) with formation redshifts z f ≲ 9 and includes a potential record-holding massive QG at zphot=5.33−0.17+0.16 and two QGs with evidence for significant residual dust content (A V ∼ 1–2). In addition, we present a large sample of 12 log M ⋆/M ⊙ = 8.5–9.5 PSBs, demonstrating that UVJ selection can be extended to low mass. An analysis of the environment of our sample reveals that the group known as the Cosmic Rose contains a massive QG and a dust-obscured star-forming galaxy (a so-called Jekyll and Hyde pair) plus three additional QGs within ∼20 kpc. Moreover, the Cosmic Rose is part of a larger overdensity at z ∼ 3.7, which contains 7/12 of our low-mass PSBs. Another four low-mass PSBs are members of an overdensity at z ∼ 3.4; this result strongly indicates low-mass PSBs are preferentially associated with overdense environments at z > 3.

Detection of strong spectral features from asymptotic-giant-branch stars in distant quiescent galaxies

Detection of strong spectral features from asymptotic-giant-branch stars in distant quiescent galaxies

Strong spectral features from asymptotic giant branch stars in distant quiescent galaxies

Strong spectral features from asymptotic giant branch stars in distant quiescent galaxies

Deciphering the properties of UV upturn galaxies in the Virgo cluster

Abstract The UV upturn refers to the increase in UV flux at wavelengths shorter than 3000 Å observed in quiescent early-type galaxies (ETGs), which still remains a puzzle. In this study, we aim to identify ETGs showing the UV upturn phenomenon within the Virgo galaxy cluster. We utilized a color-color diagram to identify all potential possible UV upturn galaxies. The Spectral Energy Distributions (SED) of these galaxies were then analyzed using the CIGALE software; we confirmed the presence of UV upturn in galaxies within the Virgo cluster. We found that the SED fitting method is the best tool to visualize and confirm the UV upturn phenomenon in ETGs. Our findings reveal that the population distributions regarding stellar mass and star formation rate properties are similar between UV upturn and red sequence galaxies. We suggest that the UV contribution originates from old stellar populations and can be modeled effectively without a burst model. Moreover, by estimating the temperature of the stellar population responsible for the UV emission, we determined it to be 13,000 K to 18,000 K. These temperature estimates support the notion that the UV upturn likely arises from the contribution of low mass evolved stellar populations (extreme horizontal branch stars). Furthermore, the Mg2 index, a metallicity indicator, in the confirmed upturn galaxies shows higher strength and follows a similar trend to previous studies. This study sheds light on the nature of UV upturn galaxies within the Virgo cluster and provides evidence that low-mass evolved stellar populations are the possible mechanisms driving the UV upturn phenomenon.

On the origin of star formation quenching in massive galaxies at ≳ in the cosmological simulations IllustrisTNG

ABSTRACT Using the cosmological simulations IllustrisTNG, we perform a comprehensive analysis of quiescent, massive galaxies at $z \gtrsim 3$. The goal is to understand what suppresses their star formation so early in cosmic time, and how other similar mass galaxies remain highly star forming. As a first-order result, the simulations are able to produce massive, quiescent galaxies in this high-redshift regime. We find that active galactic nucleus (AGN) feedback is the primary cause of halting star formation in early, massive galaxies. Not only do the central, supermassive black holes (SMBHs) of the quenched galaxies have earlier seed times, but they also grow faster than in star-forming galaxies. As a result, the quenched galaxies are exposed to AGN feedback for longer, and experience the kinetic, jet mode of the AGN feedback earlier than the star-forming galaxies. The release of kinetic energy reduces inflows of gas while likely maintaining outflows, which keeps a low cold gas fraction and decreases the star formation of the galaxies down to a state of quiescence. In addition to AGN feedback, we also investigate the influence of the large-scale environment. While mergers do not play a significant role in the quenching process, the quenched galaxies tend to reside in more massive haloes and denser regions during their evolution. As this provides a greater initial amount of infalling gas to the galaxies, the large-scale environment can mildly affect the fate of the central SMBH growth and, via AGN feedback, contribute to star formation quenching.

JWST/NIRSpec spectroscopy of intermediate-mass quiescent galaxies at z ~ 3-4

ABSTRACT We present the analysis of three intermediate-mass quiescent galaxies (QGs) with stellar masses of ${\sim} 10^{10}\, \mathrm{M}_{\odot }$ at redshifts $z\sim 3\!-\!4$ using NIRSpec low-resolution spectroscopy. Utilizing the spectral energy distribution fitting code bagpipes, we confirm these target galaxies are consistent with quiescent population, with their specific star formation rates falling below 2 dex the star-forming main sequence at the same redshifts. Additionally, we identify these QGs to be less massive than those discovered in previous works, particularly prior to the JWST era. Two of our target galaxies exhibit the potentially blended $\mathrm{ H} \, {\alpha }$ + [N ii] emission line within their spectra with signal-to-noise ratio ${\gt} 5$. We discuss whether this feature comes from an active galactic nucleus (AGN) or star formation, although future high-resolution spectroscopy is required to reach a conclusion. One of the target galaxies is covered by JWST/NIRCam imaging of the Public Release IMaging for Extragalactic Research survey. Using the 2D profile fitting code galfit, we examine its morphology, revealing a disc-like profile with a Sérsic index of $n=1.1 \pm 0.1$. On the size–mass relation, we find a potential distinction between less massive ($\log _{10}{(M_*/\mathrm{M}_\odot)}\lt 10.3$) and massive ($\log _{10}{(M_*/\mathrm{M}_\odot)}\gt 10.3$) QGs in their evolutionary pathways. The derived quenching time-scales for our targets are less than $1 \, {\rm Gyr}$. This may result from these galaxies being quenched by AGN feedback, supporting the AGN scenario of the emission line features.

Retrieval of the physical parameters of galaxies from WEAVE-StePS-like data using machine learning

Context. The William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) is a new, massively multiplexing spectrograph that allows us to collect about one thousand spectra over a 3 square degree field in one observation. The WEAVE Stellar Population Survey (WEAVE-StePS) in the next 5 years will exploit this new instrument to obtain high-S/N spectra for a magnitude-limited (IAB = 20.5) sample of ∼25 000 galaxies at moderate redshifts (z ≥ 0.3), providing insights into galaxy evolution in this as yet unexplored redshift range. Aims. We aim to test novel techniques for retrieving the key physical parameters of galaxies from WEAVE-StePS spectra using both photometric and spectroscopic (spectral indices) information for a range of noise levels and redshift values. Methods. We simulated ∼105 000 galaxy spectra assuming star formation histories with an exponentially declining star formation rate, covering a wide range of ages, stellar metallicities, specific star formation rates (sSFRs), and dust extinction values. We considered three redshifts (i.e. z = 0.3, 0.55, and 0.7), covering the redshift range that WEAVE-StePS will observe. We then evaluated the ability of the random forest and K-nearest neighbour algorithms to correctly predict the average age, metallicity, sSFR, dust attenuation, and time since the bulk of formation, assuming no measurement errors. We also checked how much the predictive ability deteriorates for different noise levels, with S/NI,obs = 10, 20, and 30, and at different redshifts. Finally, the retrieved sSFR was used to classify galaxies as part of the blue cloud, green valley, or red sequence. Results. We find that both the random forest and K-nearest neighbour algorithms accurately estimate the mass-weighted ages, u-band-weighted ages, and metallicities with low bias. The dispersion varies from 0.08–0.16 dex for age and 0.11–0.25 dex for metallicity, depending on the redshift and noise level. For dust attenuation, we find a similarly low bias and dispersion. For the sSFR, we find a very good constraining power for star-forming galaxies, log sSFR ≳ −11, where the bias is ∼0.01 dex and the dispersion is ∼0.10 dex. However, for more quiescent galaxies, with log sSFR ≲ −11, we find a higher bias, ranging from 0.61 to 0.86 dex, and a higher dispersion, ∼0.4 dex, depending on the noise level and redshift. In general, we find that the random forest algorithm outperforms the K-nearest neighbours. Finally, we find that the classification of galaxies as members of the green valley is successful across the different redshifts and S/Ns. Conclusions. We demonstrate that machine learning algorithms can accurately estimate the physical parameters of simulated galaxies for a WEAVE-StePS-like dataset, even at relatively low S/NI, obs = 10 per Å spectra with available ancillary photometric information. A more traditional approach, Bayesian inference, yields comparable results. The main advantage of using a machine learning algorithm is that, once trained, it requires considerably less time than other methods.

UNCOVER NIRSpec/PRISM Spectroscopy Unveils Evidence of Early Core Formation in a Massive, Centrally Dusty Quiescent Galaxy at z spec = 3.97

We report the spectroscopic confirmation of a massive ( log(M⋆/M⊙)=10.34±0.070.06 ), Hubble Space Telescope–dark (m F150W − m F444W = 3.6) quiescent galaxy at z spec = 3.97 in the UNCOVER survey. NIRSpec/PRISM spectroscopy and a nondetection in deep Atacama Large Millimeter/submillimeter Array imaging surprisingly reveals that the galaxy is consistent with a low (<10 M ⊙ yr−1) star formation rate (SFR) despite evidence for moderate dust attenuation. The F444W image is well modeled with a two-component Sérsic fit that favors a compact, r e ∼ 200 pc, n ∼ 2.9 component and a more extended, r e ∼ 1.6 kpc, n ∼ 1.7 component. The galaxy exhibits strong color gradients: the inner regions are significantly redder than the outskirts. Spectral energy distribution models that reproduce both the red colors and low SFR in the center of UNCOVER 18407 require both significant (A v ∼ 1.4 mag) dust attenuation and a stellar mass-weighted age of 900 Myr, implying 50% of the stars in the core already formed by z = 7.5. Using spatially resolved annular mass-to-light measurements enabled by the galaxy’s moderate magnification ( μ=2.12±0.010.05 ) to reconstruct a radial mass profile from the best-fitting two-component Sérsic model, we infer a total mass-weighted reff=0.74±0.170.22 kpc and log (Σ1kpc[M⊙kpc-2])=9.65±0.150.12 . The early formation of a dense, low SFR, and dusty core embedded in a less attenuated stellar envelope suggests an evolutionary link between the earliest-forming massive galaxies and their elliptical descendants. Furthermore, the disparity between the global, integrated dust properties and the spatially resolved gradients highlights the importance of accounting for radially varying stellar populations when characterizing the early growth of galaxy structure.

Exploring the Origin of Cold Gas and Star Formation in a Rare Population of Strongly Bulge-dominated Early-type Galaxies

We analyze the properties of a rare population, the strongly bulge-dominated early-type galaxies (sBDEs) with significant H i gas, using the databases from the FAST All Sky H i survey (FASHI) and the Arecibo Legacy Fast ALFA (ALFALFA) survey. We select the sBDEs from the Sloan Digital Sky Survey and crossmatch with the FASHI-ALFALFA combined H i sample, resulting in 104 H i-rich sBDEs. These sBDEs tend to have extremely high H i reservoirs, which is rare in previous studies such as ATLAS3D. A total of 70% of the selected sBDEs are classified as quiescent galaxies, even though they have a large H i reservoir. We study the properties of these sBDEs from four main aspects: stellar population, gas-phase metallicity, stacked H i spectra, and environment. The majority of H i-rich sBDEs appear to show lower gas-phase metallicity and are located in significantly lower-density environments, suggesting an external origin for their H i gas. We find that star-forming sBDEs exhibit statistically higher star formation efficiency and slightly older stellar populations compared to normal star-forming galaxies, suggesting a recent star formation on the Gyr timescale. They also show narrower and more concentrated H i profiles compared to control star-forming galaxies, which may explain their higher star formation efficiency.

A new perspective on the stellar mass-metallicity relation of quiescent galaxies from the LEGA-C survey

We investigated the stellar mass-metallicity relation (MZR) using a sample of 637 quiescent galaxies with 10.4 ≤ log(M*/M⊙) &lt; 11.7 selected from the LEGA-C survey at 0.6 ≤ z ≤ 1. We derived mass-weighted stellar metallicities using full-spectral fitting. We find that while lower-mass galaxies are both metal-rich and metal-poor, there are no metal-poor galaxies at high masses, and that metallicity is bounded at low values by a mass-dependent lower limit. This lower limit increases with mass, empirically defining a MEtallicity-Mass Exclusion (MEME) zone. We find that the spectral index MgFe ≡ √Mgb × Fe4383, a proxy for the stellar metallicity, also shows a mass-dependent lower limit resembling the MEME relation. Crucially, MgFe is independent of stellar population models and fitting methods. By constructing the metallicity enrichment histories, we find that, after the first gigayear, the star formation history of galaxies has a mild impact on the observed metallicity distribution. Finally, from the average formation times, we find that galaxies populate differently the metallicity-mass plane at different cosmic times, and that the MEME limit is recovered by galaxies that formed at z ≥ 3. Our work suggests that the stellar metallicity of quiescent galaxies is bounded by a lower limit which increases with the stellar mass. On the other hand, low-mass galaxies can have metallicities as high as galaxies ∼1 dex more massive. This suggests that, at log(M*/M⊙)≥10.4, rather than lower-mass galaxies being systematically less metallic, the observed MZR might be a consequence of the lack of massive metal-poor galaxies.

JWST Reveals Bulge-dominated Star-forming Galaxies at Cosmic Noon

Hubble Space Telescope imaging shows that most star-forming galaxies at cosmic noon—the peak of cosmic star formation history—appear disk-dominated, leaving the origin of the dense cores in their quiescent descendants unclear. With the James Webb Space Telescope’s high-resolution imaging to 5 μm, we can now map the rest-frame near-infrared emission, a much closer proxy for stellar mass distribution, in these massive galaxies. We selected 70 star-forming galaxies with 10 < log(M) < 12 and 1.5 < z < 3 in the CEERS survey and compare their morphologies in the rest-frame optical to those in the rest-frame near-IR. While the bulk of these galaxies are disk-dominated in 1.5 μm (rest-frame optical) imaging, they appear more bulge-dominated at 4.4 μm (rest-frame near-infrared). Our analysis reveals that in massive star-forming galaxies at z ∼ 2, the radial surface brightness profiles steepen significantly, from a slope of ∼0.3 dex−1 at 1.5 μm to ∼1.4 dex−1 at 4.4 μm within radii <1 kpc. Additionally, we find their total flux contained within the central 1 kpc is approximately 7 times higher in F444W than in F150W. In rest-optical emission, a galaxy’s central surface density appears to be the strongest indicator of whether it is quenched or star-forming. Our most significant finding is that at redder wavelengths, the central surface density ratio between quiescent and star-forming galaxies dramatically decreases from ∼10 to ∼1. This suggests the high central densities associated with galaxy quenching are already in place during the star-forming phase, imposing new constraints on the transition from star formation to quiescence.

The Velocity Dispersion Function for Quiescent Galaxies in Massive Clusters from IllustrisTNG

We derive the central stellar velocity dispersion function (VDF) for quiescent galaxies in 280 massive clusters with log(M200/M⊙)>14 in IllustrisTNG300. The VDF is an independent tracer of the dark matter mass distribution of subhalos in galaxy clusters. Based on the IllustrisTNG cluster catalog, we select quiescent member subhalos with a specific star formation rate <2 × 10−11 yr−1 and stellar mass log(M*/M⊙)>9 . We then simulate fiber spectroscopy to measure the stellar velocity dispersion of the simulated galaxies; we compute the line-of-sight velocity dispersions of star particles within a cylindrical volume that penetrates the core of each subhalo. We construct the VDFs for quiescent subhalos within R 200. The simulated cluster VDF exceeds the simulated field VDF for logσ*>2.2 , indicating the preferential formation of large velocity dispersion galaxies in dense environments. The excess is similar in simulations and in the observations. We also compare the simulated VDF for the three most massive clusters with log(M200/M⊙)>15 with the observed VDF for the two most massive clusters in the local Universe, Coma and A2029. Intriguingly, the simulated VDFs are significantly lower for logσ*>2.0 . This discrepancy results from (1) a smaller number of subhalos with log(M*/M⊙)>10 in TNG300 compared to the observed clusters, and (2) a significant offset between the observed and simulated M *–σ * relations. The consistency in the overall shape of the observed and simulated VDFs offers a unique window into galaxy and structure formation in simulations.

The JWST-SUSPENSE Ultradeep Spectroscopic Program: Survey Overview and Star Formation Histories of Quiescent Galaxies at 1 < z < 3

We present an overview and first results from the Spectroscopic Ultradeep Survey Probing Extragalactic Near-infrared Stellar Emission (SUSPENSE), executed with NIRSpec on JWST. The primary goal of the SUSPENSE program is to characterize the stellar, chemical, and kinematic properties of massive quiescent galaxies at cosmic noon. In a single deep NIRSpec/MSA configuration, we target 20 distant quiescent galaxy candidates (z = 1–3, H AB ≤ 23), as well as 53 star-forming galaxies at z = 1–4. With 16 hr of integration and the G140M-F100LP dispersion-filter combination, we observe numerous Balmer and metal absorption lines for all quiescent candidates. We derive stellar masses (logM */M ⊙ ∼ 10.2–11.5) and detailed star formation histories (SFHs) and show that all 20 candidate quiescent galaxies indeed have quenched stellar populations. These galaxies show a variety of mass-weighted ages (0.8–3.3 Gyr) and star formation timescales (∼0.5–4 Gyr), and four out of 20 galaxies were already quiescent by z = 3. On average, the z > 1.75 [z < 1.75] galaxies formed 50% of their stellar mass before z = 4 [z = 3]. Furthermore, the typical SFHs of the galaxies in these two redshift bins (z mean = 2.2 [1.3]) indicate that galaxies at higher redshift formed earlier and over shorter star formation timescales compared to lower redshifts. Although this evolution is naturally explained by the growth of the quiescent galaxy population over cosmic time, number density calculations imply that mergers and/or late-time star formation also contribute to the evolution. In future work, we will further unravel the early formation, quenching, and late-time evolution of these galaxies by extending this work with studies on their chemical abundances, resolved stellar populations, and kinematics.

A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z = 3

AbstractThe most massive galaxies in the Universe stopped forming stars due to the time-integrated feedback from central supermassive black holes (SMBHs). However, the exact quenching mechanism is not yet understood, because local massive galaxies were quenched billions of years ago. Here we present JWST/NIRSpec integral-field spectroscopy observations of GS-10578, a massive, quiescent galaxy at redshift z = 3.064 ± 0.002. From its spectrum, we measure a stellar mass M⋆ = 1.6 ± 0.2 × 1011 M⊙ and a dynamical mass Mdyn = 2.0 ± 0.5 × 1011 M⊙. Half of its stellar mass formed at z = 3.7–4.6, and the system is now quiescent, with a current star-formation rate of less than 19 M⊙ yr−1. We detect ionized- and neutral-gas outflows traced by [O iii] emission and Na i absorption, with mass outflow rates 0.14–2.9 and 30–100 M⊙ yr−1, respectively. Outflow velocities reach vout ≈ 1,000 km s−1, comparable to the galaxy escape velocity. GS-10578 hosts an active galactic nucleus, evidence that these outflows are due to SMBH feedback. The neutral outflow rate is higher than the star-formation rate. Hence, this is direct evidence for ejective SMBH feedback, with a mass loading capable of interrupting star formation by rapidly removing its fuel. Stellar kinematics show ordered rotation, with spin parameter $${\lambda }_{{{{R}}}_{{\rm{e}}}}=0.62\pm 0.07$$ λ R e = 0.62 ± 0.07 , meaning GS-10578 is rotation-supported. This study presents direct evidence for ejective active galactic nucleus feedback in a massive, recently quenched galaxy, thus helping to clarify how SMBHs quench their hosts. The high value of $${\lambda }_{{{{R}}}_{{\rm{e}}}}$$ λ R e implies that quenching can occur without destroying the stellar disk.

The JWST EXCELS survey: too much, too young, too fast? Ultra-massive quiescent galaxies at 3 &amp;lt; z &amp;lt; 5

ABSTRACT We report ultra-deep, medium-resolution spectroscopic observations for four quiescent galaxies with log$_{10}(M_*/\mathrm{M_\odot })\gt 11$ at $3 \lt z \lt 5$. These data were obtained with JWST NIRSpec as part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey, which we introduce in this work. The first two galaxies are newly selected from PRIMER UDS imaging, both at $z=4.62$ and separated by 860 pkpc on the sky, within a larger structure for which we confirm several other members. Both formed at $z\simeq 8-10$. These systems could plausibly merge by the present day to produce a local massive elliptical galaxy. The other two ultra-massive quiescent galaxies are previously known at $z=3.99$ and 3.19, with the latter (ZF-UDS-7329) having been the subject of debate as potentially too old and too massive to be accommodated by the $\Lambda$-CDM halo-mass function. Both exhibit high stellar metallicities, and for ZF-UDS-7329 we are able to measure the $\alpha -$enhancement, obtaining [Mg/Fe] = $0.42^{+0.19}_{-0.17}$. We finally evaluate whether these four galaxies are consistent with the $\Lambda$-CDM halo-mass function using an extreme value statistics approach. We find that the $z=4.62$ objects and the $z=3.19$ object are unlikely within our area under the assumption of standard stellar fractions ($f_*\simeq 0.1-0.2$). However, these objects roughly align with the most massive galaxies expected under the assumption of 100 per cent conversion of baryons to stars ($f_*$=1). Our results suggest extreme galaxy formation physics during the first billion years, but no conflict with $\Lambda$-CDM cosmology.

The Size–Mass Relation at Rest-frame 1.5 μm from JWST/NIRCam in the COSMOS-WEB and PRIMER-COSMOS Fields

We present the galaxy stellar mass–size relation in the rest-frame near-IR (1.5 μm) and its evolution with redshift up to z = 2.5. Sérsic profiles are measured for ∼26,000 galaxies with stellar masses M ⋆ > 109 M ⊙ from JWST/NIRCam F277W and F444W imaging provided by the COSMOS-WEB and PRIMER surveys using coordinates, redshifts, colors, and stellar mass estimates from the COSMOS2020 catalog. The new rest-frame near-IR effective radii are generally smaller than previously measured rest-frame optical sizes, on average by 0.14 dex, with no significant dependence on redshift. For quiescent galaxies, this size offset does not depend on stellar mass, but for star-forming galaxies, the offset increases from −0.1 dex at M ⋆ = 109.5 M ⊙ to −0.25 dex at M ⋆ > 1011 M ⊙. That is, we find that the near-IR stellar mass–size relation for star-forming galaxies is flatter in the rest-frame near-IR than in the rest-frame optical at all redshifts 0.5 < z < 2.5. The general pace of size evolution is the same in the near-IR as previously demonstrated in the optical, with slower evolution (R e ∝ (1 + z)−0.7) for L* star-forming galaxies and faster evolution (R e ∝ (1 + z)−1.3) for L* quiescent galaxies. Massive (M ⋆ > 1011 M ⊙) star-forming galaxies evolve in size almost as fast as quiescent galaxies. Low-mass (M ⋆ < 1010 M ⊙) quiescent galaxies evolve as slow as star-forming galaxies. Our main conclusion is that the size evolution narrative as it has emerged over the past two decades does not radically change when accessing the rest-frame near-IR with JWST, a better proxy of the underlying stellar mass distribution.

The fundamental plane of black hole activity for low-luminosity radio active galactic nuclei across 0 &lt; z &lt; 4

Context. The fundamental plane of black hole activity describes the correlation between radio luminosity (LR), X-ray luminosity (LX), and black hole mass (MBH). It reflects a connection between the accretion disc and the jet. However, the dependence of the fundamental plane on various physical properties of active galactic nuclei (AGNs) and host galaxies remains unclear, especially for low-luminosity AGNs, which is important for understanding the accretion physics in AGNs. Aims. Here, we explore the dependence of the fundamental plane on the radio loudness, Eddington-ratio (λEdd), redshift, and galaxy star formation properties (star-forming galaxies and quiescent galaxies) across 0.1 &lt; z ≤ 4 for radio AGNs. Based on current deep and large surveys, our studies can extend to lower luminosities and higher redshifts. Methods. From the deep and large multi-wavelength surveys in the GOODS-N, GOODS-S, and COSMOS/UltraVISTA fields, we constructed a large and homogeneous radio AGN sample consisting of 208 objects with available estimates for LR and LX. Then we divided the radio AGN sample into 141 radio-quiet AGNs and 67 radio-loud AGNs according to the radio loudness defined by the ratio of LR to LX, and explored the dependence of the fundamental plane on different physical properties of the two populations, separately. Results. The ratio of LR to LX shows a bimodal distribution that is well described by two single Gaussian models. The cross point between these two Gaussian components corresponds to a radio-loudness threshold of log(LR/LX) = − 2.73. The radio-quiet AGNs have a significantly larger Eddington ratio than the radio-loud AGNs. Our radio-quiet and radio-loud AGNs show a significantly different fundamental plane, which indicates a significant dependence of the fundamental plane on the radio loudness. For both radio-quiet and radio-loud AGNs, the fundamental plane shows a significant dependence on λEdd, but no dependence on redshift. The fundamental plane shows a significant dependence on the galaxy star formation properties for radio-quiet AGNs, while for radio-loud AGNs this dependence disappears. Conclusions. The fundamental plane sheds important light on the accretion physics and X-ray emission origins of central engines. X-ray emission of radio-quiet AGNs at 0.01 &lt; λEdd &lt; 0.1 are produced by a combination of advection-dominated accretion flow (ADAF) and synchrotron radiation from the jet, while at 0.1 &lt; λEdd &lt; 1 they mainly follow the synchrotron jet model. The origins of X-ray emission of radio-loud AGNs are consistent with a combination of ADAF and the synchrotron jet model at λEdd &lt; 0.01, agree with the synchrotron jet model at 0.01 &lt; λEdd &lt; 0.1, and follow a combination of the standard thin disc and a jet model at λEdd &gt; 0.1.

Massive Quiescent Disk Galaxies at 0.5 ≤ z ≤ 1 in CANDELS: Color Gradients and Likely Origin

A rare population of massive disk-dominated quiescent galaxies has recently drawn much attention, which intrudes the red sequence (RS) population without destroying the underlying stellar disks. In this study, we have carefully identified 48 RS, disk-dominated galaxies with M * > 1010 M ⊙ between redshift 0.5 and 1.0 in all five CANDELS fields. These galaxies are well fitted by a two-component bulge plus disk model, and have the bulge-to-total ratio B/T < 0.4 in the both F814W and F160W bands. The fitting results indicate that these galaxies generally have extended stellar disks (∼3 kpc on average) and tiny bulge components (∼0.5 kpc on average). To understand their possible origins, we have also selected two control samples of 156 green valley (GV) and 309 blue cloud (BC) disk-dominated galaxies according to the same selection criteria. We study the UVI(U − V versus V − I) color gradients of these galaxies to infer their specific star formation rate (sSFR) gradients out to the maximum acceptable radii. We show that on average the disks in disk-dominated RS galaxies are fully quenched at all radii, whereas both the BC and GV disks are not fully quenched at any radii. We find that all the BC, GV, and RS disk galaxies generally have nearly flat sSFR profiles. We propose a potential formation mechanism, acknowledging that various other mechanisms (e.g., central compaction and active galactic nucleus feedback) might contribute, where massive quiescent disk-dominated galaxies are predominantly formed via a process of secular disk fading.

Reconciling M/L Ratios Across Cosmic Time: a Concordance IMF for Massive Galaxies

The stellar initial mass function (IMF) is thought to be bottom heavy in the cores of the most massive galaxies, with an excess of low-mass stars compared to the Milky Way. However, studies of the kinematics of quiescent galaxies at 2 < z < 5 find M/L ratios that indicate lighter IMFs. Light IMFs have also been proposed for the unexpected populations of luminous galaxies that JWST has uncovered at z > 7 to reduce tensions with galaxy formation models. Here we explore “ski slope” IMFs that are simultaneously bottom heavy, with a steep slope at low stellar masses, and top heavy, with a shallow slope at high masses. We derive a form of the IMF for massive galaxies that is consistent with measurements in the local universe and yet produces relatively low M/L ratios at high redshift. This concordance IMF has slopes γ 1 = 2.40 ± 0.09, γ 2 = 2.00 ± 0.14, and γ 3 = 1.85 ± 0.11 in the regimes 0.08 M ⊙ – 0.5 M ⊙, 0.5 M⊙ – 1 M ⊙, and >1 M ⊙, respectively. The IMF parameter α, the mass excess compared to a Milky Way IMF, ranges from log(α)≈+0.3 for present-day galaxies to log(α)≈−0.1 for their star-forming progenitors. The concordance IMF applies only to the central regions of the most massive galaxies, with velocity dispersions σ ∼ 300 km s−1, and their progenitors. However, it can be generalized using a previously measured relation between α and σ. We arrive at the following modification to the Kroupa (2001) IMF for galaxies with σ ≳ 160 km s−1: γ1≈1.3+4.3logσ160 , γ2≈2.3−1.2logσ160 , and γ3≈2.3−1.7logσ160 , with σ 160 = σ/160 km s−1. If galaxies grow primarily inside out, so that velocity dispersions are relatively stable, these relations should also hold at high redshift.

Different regulation of stellar metallicities between star-forming and quiescent galaxies – insights into galaxy quenching

ABSTRACT One of the most important questions in astrophysics is what causes galaxies to stop forming stars. Previous studies have shown a tight link between quiescence and black hole mass. Other studies have revealed that quiescence is also associated with ‘starvation’, the halting of gas inflows, which results in the remaining gas being used up by star formation and in rapid chemical enrichment. In this work, we find the missing link between these two findings. Using a large sample of galaxies, we uncover the intrinsic dependences of the stellar metallicity on galaxy properties. In the case of star-forming galaxies, stellar metallicity is primarily driven by stellar mass. However, for passive galaxies, the stellar metallicity is primarily driven by the stellar velocity dispersion. The latter is known to be tightly correlated with black hole mass. This result can be seen as connecting previous studies, where the integrated effect of black hole feedback (i.e. black hole mass, traced by the velocity dispersion) prevents gas inflows, starving the galaxy, which is seen by the rapid increase in the stellar metallicity, and leading to the galaxy becoming passive.