85 research outputs found
Recommended from our members
The weak imprint of environment on the stellar populations of galaxies
We investigate the environmental dependence of the stellar populations of galaxies in SDSS DR7. Echoing earlier works, we find that satellites are both more metal-rich (<0.1dex) and older (<2Gyr) than centrals of the same stellar mass. However,after separating star-forming, green valley and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03dex) and age (<0.5Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley and passive galaxies when the environmental dependence of galaxy properties are investigated.We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (‘strangulation’) contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass–stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias.ERC
STF
Adding Value to JWST Spectra and Photometry: Stellar Population and Star Formation Properties of Spectroscopically Confirmed JADES and CEERS Galaxies at
In this paper, we discuss measurements of the stellar population and star
forming properties for 43 spectroscopically confirmed publicly available
high-redshift JWST galaxies in the JADES and CEERS observational
programs. We carry out a thorough study investigating the relationship between
spectroscopic features and photometrically derived ones, including from
spectral energy distribution (SED) fitting of models, as well as morphological
and structural properties. We find that the star formation rates (SFRs)
measured from H line emission are higher than those estimated from
Bayesian SED fitting and UV luminosity, with ratios SFR/ SFR
ranging from 2~13. This is a sign that the star formation history is
consistently rising given the timescales of H vs UV star formation
probes. In addition, we investigate how well equivalent widths (EWs) of
H 4861, [O III] 4959, and [O III] 5007 can be
measured from photometry, finding that on average the EW derived from
photometric excesses in filters is 30% smaller than the direct spectroscopic
measurement. We also discover that a stack of the line emitting galaxies shows
a distinct morphology after subtracting imaging that contains only the
continuum. This gives us a first view of the line or ionized gas emission from
galaxies, demonstrating that this material has a similar distribution,
statistically, as the continuum. We also compare the derived SFRs and stellar
masses for both parametric and non-parametric star formation histories, where
we find that 35% of our sample formed at least 30% of their stellar mass in
recent (< 10 Myr) starburst events.Comment: 17 Pages, 13 Figures, 4 Tables, submitted to MNRA
Recommended from our members
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
EPOCHS VI: The Size and Shape Evolution of Galaxies since z ~ 8 with JWST Observations
We present the results of a size and structural analysis of 1395 galaxies at
with stellar masses
9.5 within the JWST Public CEERS field that overlaps with the HST CANDELS
EGS observations. We use GALFIT to fit single S\'ersic models to the rest-frame
optical profile of our galaxies, which is a mass-selected sample complete to
our redshift and mass limit. Our primary result is that at fixed rest-frame
wavelength and stellar mass, galaxies get progressively smaller, evolving as
up to . We discover that the vast
majority of massive galaxies at high redshifts have low S\'ersic indices, thus
do not contain steep, concentrated light profiles. Additionally, we explore the
evolution of the size-stellar mass relationship, finding a correlation such
that more massive systems are larger up to . This relationship breaks
down at , where we find that galaxies are of similar sizes, regardless
of their star formation rates and S\'ersic index, varying little with mass. We
show that galaxies are more compact at redder wavelengths, independent of sSFR
or stellar mass up to . We demonstrate the size evolution of galaxies
continues up to , showing that the process or causes for this
evolution is active at early times. We discuss these results in terms of ideas
behind galaxy formation and evolution at early epochs, such as their importance
in tracing processes driving size evolution, including minor mergers and AGN
activity.Comment: Submitted to MNRA
EPOCHS VIII. An Insight into MIRI-selected Galaxies in SMACS-0723 and the Benefits of Deep MIRI Photometry in Revealing AGN and the Dusty Universe
We present the analysis of the stellar population and star formation history
of 181 MIRI selected galaxies at redshift 0-3.5 in the massive galaxy cluster
field SMACS J0723.3-7327, commonly referred to as SMACS0723, using the James
Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI). We combine the data
with the JWST Near Infrared Camera (NIRCam) catalogue, in conjunction with the
Hubble Space Telescope (HST) WFC3/IR and ACS imaging. We find that the MIRI
bands capture PAH features and dust emission, significantly enhancing the
accuracy of photometric redshift and measurements of the physical properties of
these galaxies. The median photo-z's of galaxies with MIRI data are found to
have a small 0.1% difference from spectroscopic redshifts and reducing the
error by 20 percent. With MIRI data included in SED fits, we find that the
measured stellar masses are unchanged, while the star formation rate is
systematically lower by 0.1 dex. We also fit the median SED of active galactic
nuclei (AGN) and star forming galaxies (SFG) separately. MIRI data provides
tighter constraints on the AGN contribution, reducing the typical AGN
contributions by ~14 percent. In addition, we also compare the median SED
obtained with and without MIRI, and we find that including MIRI data yields
steeper optical and UV slopes, indicating bluer colours, lower dust
attenuation, and younger stellar populations. In the future, MIRI/MRS will
enhance our understanding by providing more detailed spectral information and
allowing for the study of specific emission features and diagnostics associated
with AGN.Comment: 15 pages, 14 figures and 1 table, submitted to MNRA
Seeing sharper and deeper: JWST's first glimpse of the photometric and spectroscopic properties of galaxies in the epoch of reionisation
We analyse the photometric and spectroscopic properties of four galaxies in
the epoch of reionisation (EoR) within the SMACS 0723 JWST Early Release
Observations field. Given the known spectroscopic redshifts of these sources,
we investigated the accuracy with which photometric redshifts can be derived
using NIRCam photometry alone, finding that F115W imaging is essential to
distinguish between z~8 galaxies with high equivalent width (EW) [O III]
{\lambda}5007 emission and z~10 Balmer break galaxies. We find that all four
sources exhibit strong (> 0.6 mag) F356W-F444W colours, which sit at the
extreme end of theoretical predictions from numerical simulations. We find that
these galaxies deviate (by roughly 0.5 dex) from the local correlation between
[O III] {\lambda}5007/H\beta and [Ne III] {\lambda}3869/[O II], which is
consistent with the predictions from simulations of high-redshift galaxies. We
measure the [O III] {\lambda}5007 rest-frame equivalent widths both directly
from the spectroscopy, and indirectly as inferred from the strong F356W-F444W
colours, finding large [O III] {\lambda}5007 EWs of 400-1000 {\AA}. The [O III]
{\lambda}5007 and H\beta EWs are consistent with those seen in extreme,
intensely star-forming dwarf galaxies in the local Universe. Our structural
analysis indicates that these galaxies are resolved, exhibiting irregular
shapes with bright clumps and colour gradients. In line with the predictions
from the FLARES hydrodynamic simulations, such intense star formation and
extreme nebular conditions are likely the norm, rather than the exception, in
the EoR. Finally, although star-forming galaxies and AGN often occupy similar
regions within the [O III] {\lambda}5007/H\beta-[O II]/H{\delta} plane, we find
that AGN exhibit distinct, red colours in the F150W-F200W, F200W-F277W plane.Comment: 14 pages, 8 figure
First Light And Reionisation Epoch Simulations (FLARES) XI: [OIII] emitting galaxies at
JWST has now made it possible to probe the rest-frame optical line emission
of high-redshift galaxies extending to z~9, and potentially beyond. To aid in
the interpretation of these emerging constraints, in this work we explore
predictions for [OIII] emission in high-redshift galaxies using the First Light
and Reionisation Epoch Simulations (FLARES). We produce predictions for the
[OIII] luminosity function, its correlation with the UV luminosity, and the
distribution of equivalent widths (EWs). We also explore how the [OIII] EW
correlates with physical properties including specific star formation rate,
metallicity, and dust attenuation. Our predictions are largely consistent with
recent observational constraints on the luminosity function, average equivalent
widths, and line ratios. However, they fail to reproduce the observed tail of
high-EW sources and the number density of extreme line emitters. Possibilities
to explain these discrepancies include an additional source of ionising photons
and/or greater stochasticity in star formation in the model or photometric
scatter and/or bias in the observations. With JWST now rapidly building larger
samples and a wider range of emission lines the answer to this remaining
discrepancy should be available imminently.Comment: 15 pages, accepted for publication in MNRAS, minor changes from
original versio
The JWST Hubble Sequence: The Rest-frame Optical Evolution of Galaxy Structure at 1.5 < z < 6.5
© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/We present results on the morphological and structural evolution of a total of 3956 galaxies observed with JWST at 1.5 109 M ⊙ at z > 3 are not dominated by irregular and peculiar structures, either visually or quantitatively, as previously thought. We find a strong dominance of morphologically selected disk galaxies up to z = 6 in this mass range. We also find that the stellar mass and star formation rate densities are dominated by disk galaxies up to z ∼ 6, demonstrating that most stars in the Universe were likely formed in a disk galaxy. We compare our results to theory to show that the fraction of types we find is predicted by cosmological simulations, and that the Hubble Sequence was already in place as early as one billion years after the Big Bang. Additionally, we make our visual classifications public for the community.Peer reviewe
EPOCHS VI: The Size and Shape Evolution of Galaxies since z ∼ 8 with JWST Observations
We present the results of a size and structural analysis of 1395 galaxies at 0.5 ≤ z ≲ 8 with stellar masses log (M*/M⊙> 9.5 within the JWST Public CEERS field that overlaps with the HST CANDELS EGS observations. We use GALFIT to fit single Sérsic models to the rest-frame optical profile of our galaxies, which is a mass-selected sample complete to our redshift and mass limit. Our primary result is that at fixed rest-frame wavelength and stellar mass, galaxies get progressively smaller, evolving as ∼(1 + z)−0.71 ± 0.19 up to z ∼ 8. We discover that the vast majority of massive galaxies at high redshifts have low Sérsic indices, thus do not contain steep, concentrated light profiles. Additionally, we explore the evolution of the size-stellar mass relationship, finding a correlation such that more massive systems are larger up to z ∼ 3. This relationship breaks down at z > 3, where we find that galaxies are of similar sizes, regardless of their star formation rates and Sérsic index, varying little with mass. We show that galaxies are more compact at redder wavelengths, independent of sSFR or stellar mass up to z ∼ 3. We demonstrate the size evolution of galaxies continues up to z ∼ 8, showing that the process or causes for this evolution is active at early times. We discuss these results in terms of ideas behind galaxy formation and evolution at early epochs, such as their importance in tracing processes driving size evolution, including minor mergers and AGN activity
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