16 research outputs found
What drives galaxy quenching? A deep connection between galaxy kinematics and quenching in the local Universe
We develop a 2D inclined rotating disc model, which we apply to the stellar
velocity maps of 1862 galaxies taken from the MaNGA survey (SDSS public Data
Release 15). We use a random forest classifier to identify the kinematic
parameters that are most connected to galaxy quenching. We find that kinematic
parameters that relate predominantly to the disc (such as the mean rotational
velocity) and parameters that characterise whether a galaxy is rotation- or
dispersion-dominated (such as the ratio of rotational velocity to velocity
dispersion) are not fundamentally linked to the quenching of star formation.
Instead, we find overwhelmingly that it is the absolute level of velocity
dispersion (a property that relates primarily to a galaxy's bulge/spheroidal
component) that is most important for separating star forming and quenched
galaxies. Furthermore, a partial correlation analysis shows that many commonly
discussed correlations between galaxy properties and quenching are spurious,
and that the fundamental correlation is between quenching and velocity
dispersion. In particular, we find that at fixed velocity dispersion, there is
only a very weak dependence of quenching on the disc properties, whereby more
discy galaxies are slightly more likely to be forming stars. By invoking the
tight relationship between black hole mass and velocity dispersion, and noting
that black hole mass traces the total energy released by AGN, we argue that
these data support a scenario in which quenching occurs by preventive feedback
from AGN. The kinematic measurements from this work are publicly available
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Are galactic star formation and quenching governed by local, global, or environmental phenomena?
We present an analysis of star formation and quenching in the SDSS-IV
MaNGA-DR15, utilising over 5 million spaxels from 3500 local galaxies. We
estimate star formation rate surface densities () via dust
corrected flux where possible, and via an empirical relationship
between specific star formation rate (sSFR) and the strength of the 4000
Angstrom break (D4000) in all other cases. We train a multi-layered artificial
neural network (ANN) and a random forest (RF) to classify spaxels into `star
forming' and `quenched' categories given various individual (and groups of)
parameters. We find that global parameters (pertaining to the galaxy as a
whole) perform collectively the best at predicting when spaxels will be
quenched, and are substantially superior to local/ spatially resolved and
environmental parameters. Central velocity dispersion is the best single
parameter for predicting quenching in central galaxies. We interpret this
observational fact as a probable consequence of the total integrated energy
from AGN feedback being traced by the mass of the black hole, which is well
known to correlate strongly with central velocity dispersion. Additionally, we
train both an ANN and RF to estimate values directly via
regression in star forming regions. Local/ spatially resolved parameters are
collectively the most predictive at estimating in these
analyses, with stellar mass surface density at the spaxel location ()
being by far the best single parameter. Thus, quenching is fundamentally a
global process but star formation is governed locally by processes within each
spaxel.ERC Advanced Grant: 695671 "Quench
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The ALMaQUEST survey IX: The nature of the resolved star forming main sequence
We investigate the nature of the scaling relations between the surface
density of star formation rate (), stellar mass (), and molecular gas mass (), aiming at distinguishing
between the relations that are primary, i.e. more fundamental, and those which
are instead an indirect by-product of the other relations. We use the ALMaQUEST
survey and analyse the data by using both partial correlations and Random
Forest regression techniques. We unambiguously find that the strongest
intrinsic correlation is between and
(i.e. the resolved Schmidt-Kennicutt relation), followed by the correlation
between and (resolved Molecular Gas Main
Sequence, rMGMS). Once these two correlations are taken into account, we find
that there is no evidence for any intrinsic correlation between and , implying that SFR is entirely driven by the amount of
molecular gas, while its dependence on stellar mass (i.e. the resolved Star
Forming Main Sequence, rSFMS) simply emerges as a consequence of the
relationship between molecular gas and stellar mass.Science and Technology Facilities Council (STFC).
ERC Advanced Grant 695671 "QUENCH"
The ALMaQUEST Survey - V. The non-universality of kpc-scale star formation relations and the factors that drive them
ABSTRACT
Using a sample of ∼15 000 kpc-scale star-forming spaxels in 28 galaxies drawn from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we investigate the galaxy-to-galaxy variation of the ‘resolved’ Schmidt–Kennicutt relation (rSK; –ΣSFR), the ‘resolved’ star-forming main sequence (rSFMS; Σ⋆–ΣSFR), and the ‘resolved’ molecular gas main sequence (rMGMS; Σ⋆–). The rSK relation, rSFMS, and rMGMS all show significant galaxy-to-galaxy variation in both shape and normalization, indicating that none of these relations is universal between galaxies. The rSFMS shows the largest galaxy-to-galaxy variation and the rMGMS the least. By defining an ‘offset’ from the average relations, we compute a ΔrSK, ΔrSFMS, ΔrMGMS for each galaxy, to investigate correlations with global properties. We find the following correlations with at least 2σ significance: The rSK is lower (i.e. lower star formation efficiency) in galaxies with higher M⋆, larger Sersic index, and lower specific SFR (sSFR); the rSFMS is lower (i.e. lower sSFR) in galaxies with higher M⋆ and larger Sersic index; and the rMGMS is lower (i.e. lower gas fraction) in galaxies with lower sSFR. In the ensemble of all 15 000 data points, the rSK relation and rMGMS show equally tight scatters and strong correlation coefficients, compared with a larger scatter and weaker correlation in the rSFMS. Moreover, whilst there is no correlation between ΔrSK and ΔrMGMS in the sample, the offset of a galaxy’s rSFMS does correlate with both of the other two offsets. Our results therefore indicate that the rSK and rMGMS are independent relations, whereas the rSFMS is a result of their combination.ERC
STF
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How do central and satellite galaxies quench? - Insights from spatially resolved spectroscopy in the MaNGA survey
We investigate how star formation quenching proceeds within central and
satellite galaxies using spatially resolved spectroscopy from the SDSS-IV MaNGA
DR15. We adopt a complete sample of star formation rate surface densities
(), derived in Bluck et al. (2020), to compute the distance
at which each spaxel resides from the resolved star forming main sequence
( relation): . We study
galaxy radial profiles in , and luminosity weighted
stellar age (), split by a variety of intrinsic and environmental
parameters. Via several statistical analyses, we establish that the quenching
of central galaxies is governed by intrinsic parameters, with central velocity
dispersion () being the most important single parameter. High mass
satellites quench in a very similar manner to centrals. Conversely, low mass
satellite quenching is governed primarily by environmental parameters, with
local galaxy over-density () being the most important single
parameter. Utilising the empirical - relation, we estimate
that quenching via AGN feedback must occur at , and is marked by steeply rising radial
profiles in the green valley, indicating `inside-out' quenching. On the other
hand, environmental quenching occurs at over-densities of 10 - 30 times the
average galaxy density at z0.1, and is marked by steeply declining
profiles, indicating `outside-in' quenching. Finally,
through an analysis of stellar metallicities, we conclude that both intrinsic
and environmental quenching must incorporate significant starvation of gas
supply.ERC
STF
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Towards robust determination of non-parametric morphologies in marginal astronomical data: Resolving uncertainties with cosmological hydrodynamical simulations
Quantitative morphologies, such as asymmetry and concentration, have long
been used as an effective way to assess the distribution of galaxy starlight in
large samples. Application of such quantitative indicators to other data
products could provide a tool capable of capturing the 2-dimensional
distribution of a range of galactic properties, such as stellar mass or
star-formation rate maps. In this work, we utilize galaxies from the Illustris
and IllustrisTNG simulations to assess the applicability of concentration and
asymmetry indicators to the stellar mass distribution in galaxies.
Specifically, we test whether the intrinsic values of concentration and
asymmetry (measured directly from the simulation stellar mass particle maps)
are recovered after the application of measurement uncertainty and a point
spread function (PSF). We find that random noise has a non-negligible
systematic effect on asymmetry that scales inversely with signal-to-noise,
particularly at signal-to-noise less than 100. We evaluate different methods to
correct for the noise contribution to asymmetry at very low signal-to-noise,
where previous studies have been unable to explore due to systematics. We
present algebraic corrections for noise and resolution to recover the intrinsic
morphology parameters. Using Illustris as a comparison dataset, we evaluate the
robustness of these fits in the presence of a different physics model, and
confirm these correction methods can be applied to other datasets. Lastly, we
provide estimations for the uncertainty on different correction methods at
varying signal-to-noise and resolution regimes.STFC
ER
Galaxy Quenching at the High Redshift Frontier: A Fundamental Test of Cosmological Models in the Early Universe with JWST-CEERS
We present an analysis of the quenching of star formation in massive galaxies (M * > 109.5 M ⊙) within the first 0.5-3 Gyr of the Universe’s history utilizing JWST-CEERS data. We utilize a combination of advanced statistical methods to accurately constrain the intrinsic dependence of quenching in a multidimensional and intercorrelated parameter space. Specifically, we apply random forest classification, area statistics, and a partial correlation analysis to the JWST-CEERS data. First, we identify the key testable predictions from two state-of-the-art cosmological simulations (IllustrisTNG and EAGLE). Both simulations predict that quenching should be regulated by supermassive black hole mass in the early Universe. Furthermore, both simulations identify the stellar potential (ϕ *) as the optimal proxy for black hole mass in photometric data. In photometric observations, where we have no direct constraints on black hole masses, we find that the stellar potential is the most predictive parameter of massive galaxy quenching at all epochs from z = 0-8, exactly as predicted by simulations for this sample. The stellar potential outperforms stellar mass, galaxy size, galaxy density, and Sérsic index as a predictor of quiescence at all epochs probed in JWST-CEERS. Collectively, these results strongly imply a stable quenching mechanism operating throughout cosmic history, which is closely connected to the central gravitational potential in galaxies. This connection is explained in cosmological models via massive black holes forming and growing in deep potential wells, and subsequently quenching galaxies through a mix of ejective and preventative active galactic nucleus feedback
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The Fundamental Signature of Star Formation Quenching from AGN Feedback: A Critical Dependence of Quiescence on Supermassive Black Hole Mass, Not Accretion Rate
Abstract
We identify the intrinsic dependence of star formation quenching on a variety of galactic and environmental parameters, utilizing a machine-learning approach with Random Forest classification. We have previously demonstrated the power of this technique to isolate causality, not mere correlation, in complex astronomical data. First, we analyze three cosmological hydrodynamical simulations (Eagle, Illustris, and IllustrisTNG), selecting snapshots spanning the bulk of cosmic history from comic noon (z ∼ 2) to the present epoch, with stellar masses in the range
9
<
log
(
M
*
/
M
⊙
)
<
12
. In the simulations, black hole mass is unanimously found to be the most predictive parameter of central galaxy quenching at all epochs. Perhaps surprisingly, black hole accretion rate (and hence the bolometric luminosity of active galactic nuclei, AGN) is found to be of little predictive power over quenching. This theoretical result is important for observational studies of galaxy quenching, as it cautions against using the current AGN state of a galaxy as a useful proxy for the cumulative impact of AGN feedback on a galactic system. The latter is traced by black hole mass, not AGN luminosity. Additionally, we explore a subset of “observable” parameters, which can be readily measured in extant wide-field galaxy surveys targeting z = 0–2, at
9
<
log
(
M
*
/
M
⊙
)
<
12
. All three simulations predict that, in lieu of black hole mass, the stellar gravitational potential will outperform the other parameters in predicting quenching. We confirm this theoretical prediction observationally in the SDSS (at low redshifts) and in CANDELS (at intermediate and high redshifts).ERC Advanced Grant 695671: ‘QUENCH’
Science and Technology Facilities Council (STFC),
Royal Society Research Professorshi
On the quenching of star formation in observed and simulated central galaxies: evidence for the role of integrated AGN feedback
In this paper we investigate how massive central galaxies cease their star
formation by comparing theoretical predictions from cosmological simulations:
EAGLE, Illustris and IllustrisTNG with observations of the local Universe from
the Sloan Digital Sky Survey (SDSS). Our machine learning (ML) classification
reveals supermassive black hole mass () as the most predictive
parameter in determining whether a galaxy is star forming or quenched at
redshift in all three simulations. This predicted consequence of active
galactic nucleus (AGN) quenching is reflected in the observations, where it is
true for a range of indirect estimates of via proxies as well as
its dynamical measurements. Our partial correlation analysis shows that other
galactic parameters lose their strong association with quiescence, once their
correlations with are accounted for. In simulations we demonstrate
that it is the integrated power output of the AGN, rather than its
instantaneous activity, which causes galaxies to quench. Finally, we analyse
the change in molecular gas content of galaxies from star forming to passive
populations. We find that both gas fractions () and star formation
efficiencies (SFEs) decrease upon transition to quiescence in the observations
but SFE is more predictive than in the ML passive/star-forming
classification. These trends in the SDSS are most closely recovered in
IllustrisTNG and are in direct contrast with the predictions made by Illustris.
We conclude that a viable AGN feedback prescription can be achieved by a
combination of preventative feedback and turbulence injection which together
quench star formation in central galaxies
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Towards a deeper understanding of the physics driving galaxy quenching - Inferring trends in the gas content via extinction
In order to investigate the importance of different proposed quenching
mechanisms, we use an indirect method to estimate gas masses for ~62,000 SDSS
DR7 galaxies. We infer gas surface densities from dust column densities as
traced by extinction within the fibre, applying a metallicity correction to
account for varying dust-to-gas ratios. We find that both gas fraction and star
formation efficiency (SFE) decrease moving away from the star forming main
sequence (MS) towards quiescence for all galaxy masses. We further show that
both quantities correlate similarly strongly with the departure from the MS,
implying the need for any physical model of quenching to invoke a change in
gas fraction and SFE. Our results call for a better
understanding of the physical processes driving the decrease in star formation
efficiency, which has received relatively little attention in the theory of
quenching until now