18 research outputs found
A rest-frame near-IR study of clumps in galaxies at 1 < z < 2 using JWST/NIRCam: connection to galaxy bulges
A key question in galaxy evolution has been the importance of the apparent
`clumpiness' of high redshift galaxies. Until now, this property has been
primarily investigated in rest-frame UV, limiting our understanding of their
relevance. Are they short-lived or are associated with more long-lived massive
structures that are part of the underlying stellar disks? We use JWST/NIRCam
imaging from CEERS to explore the connection between the presence of these
`clumps' in a galaxy and its overall stellar morphology, in a mass-complete
() sample of galaxies at .
Exploiting the uninterrupted access to rest-frame optical and near-IR light, we
simultaneously map the clumps in galactic disks across our wavelength coverage,
along with measuring the distribution of stars among their bulges and disks.
Firstly, we find that the clumps are not limited to rest-frame UV and optical,
but are also apparent in near-IR with spatial overlap. This
rest-frame near-IR detection indicates that clumps would also feature in the
stellar-mass distribution of the galaxy. A secondary consequence is that these
will hence be expected to increase the dynamical friction within galactic disks
leading to gas inflow. We find a strong negative correlation between how clumpy
a galaxy is and strength of the bulge. This firmly suggests an evolutionary
connection, either through clumps driving bulge growth, or the bulge
stabilizing the galaxy against clump formation, or a combination of the two.
Finally, we find evidence of this correlation differing from rest-frame optical
to near-IR, which could suggest a combination of varying formation modes for
the clumps.Comment: Accepted for publication in Ap
Feedback factory : multiple faint radio jets detected in a cluster at z=2
We report the detection of multiple faint radio sources, that we identify as active galactic nucleus (AGN) jets, within CLJ1449+0856 at z = 2 using 3 GHz Very Large Array observations. We study the effects of radio-jet-based kinetic feedback at high redshifts, which has been found to be crucial in low-redshift clusters to explain the observed thermodynamic properties of their intracluster medium (ICM). We investigate this interaction at an epoch featuring high levels of AGN activity and a transitional phase of ICM in regards to the likelihood of residual cold gas accretion. We measure a total flux of 30.6 +/- 3.3 mu Jy from the six detected jets. Their power contribution is estimated to be 1.2 (+/- 0.6) x 10(44) erg s(-1), although this value could be up to 4.7 x 10(44) erg s(-1). This is a factor of similar to 0.25-1.0 of the previously estimated instantaneous energy injection into the ICM of CLJ1449+0856 from AGN outflows and star formation that have already been found to be sufficient in globally offsetting the cooling flows in the cluster core. In line with the already detected abundance of star formation, this mode of feedback being distributed over multiple sites, contrary to a single central source observed at low redshifts, points to accretion of gas into the cluster centre. This also suggests a 'steady state' of the cluster featuring non-cool-core-like behaviour. Finally, we also examine the total infrared-radio luminosity ratio for the known sample of galaxies within the cluster core and find that dense environments do not have any serious consequence on the compliance of galaxies to the infrared-radio correlation.Peer reviewe
Fitting pseudo-Sérsic (Spergel) light profiles to galaxies in interferometric data: The excellence of the uυ-plane
Modern (sub)millimeter interferometers, such as ALMA and NOEMA, offer high angular resolution and unprecedented sensitivity. This provides the possibility to characterize the morphology of the gas and dust in distant galaxies. To assess the capabilities of the current software in recovering morphologies and surface brightness profiles in interferometric observations, we tested the performance of the Spergel model for fitting in the uυ-plane, which has been recently implemented in the IRAM software GILDAS (uv_fit). Spergel profiles provide an alternative to the Sérsic profile, with the advantage of having an analytical Fourier transform, making them ideal for modeling visibilities in the uυ-plane. We provide an approximate conversion between the Spergel index and the Sérsic index, which depends on the ratio of the galaxy size to the angular resolution of the data. We show through extensive simulations that Spergel modeling in the uυ-plane is a more reliable method for parameter estimation than modeling in the image plane, as it returns parameters that are less affected by systematic biases and results in a higher effective signal-to-noise ratio. The better performance in the uυ-plane is likely driven by the difficulty of accounting for a correlated signal in interferometric images. Even in the uυ-plane, the integrated source flux needs to be at least 50 times larger than the noise per beam to enable a reasonably good measurement of a Spergel index. We characterized the performance of Spergel model fitting in detail by showing that parameter biases are generally low (<10%) and that uncertainties returned by uv_fit are reliable within a factor of two. Finally, we showcase the power of Spergel fitting by reexamining two claims of extended halos around galaxies from the literature, showing that galaxies and halos can be successfully fitted simultaneously with a single Spergel model
IllustrisTNG in the HSC-SSP: image data release and the major role of mini mergers as drivers of asymmetry and star formation
At fixed galaxy stellar mass, there is a clear observational connection
between structural asymmetry and offset from the star forming main sequence,
SFMS. Herein, we use the TNG50 simulation to investigate the relative
roles of major mergers (stellar mass ratios ), minor (), and mini mergers () in driving this
connection amongst star forming galaxies (SFGs). We use dust radiative transfer
post-processing with SKIRT to make a large, public collection of synthetic
Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) images of simulated TNG
galaxies over with (k images). Using their instantaneous SFRs,
known merger histories/forecasts, and HSC-SSP asymmetries, we show (1) that
TNG50 SFGs qualitatively reproduce the observed trend between SFMS and
asymmetry and (2) a strikingly similar trend emerges between SFMS and
the time-to-coalescence for mini mergers. Controlling for redshift, stellar
mass, environment, and gas fraction, we show that individual mini merger events
yield small enhancements in SFRs and asymmetries that are sustained on long
timescales (at least Gyr after coalescence, on average) -- in contrast
to major/minor merger remnants which peak at much greater amplitudes but are
consistent with controls only Gyr after coalescence. Integrating the
boosts in SFRs and asymmetries driven by mergers since in
TNG50 SFGs, we show that mini mergers are responsible for (i) per cent of
all merger-driven star formation and (ii) per cent of merger-driven
asymmetric structure. Due to their relative frequency and prolonged boost
timescales, mini mergers dominate over their minor and major counterparts in
driving star formation and asymmetry in SFGs.Comment: 32 pages; 18 figures; submitted to MNRAS; Image data available via
the TNG website: www.tng-project.org/bottrell2
JWST and ALMA discern the assembly of structural and obscured components in a high-redshift starburst galaxy
We present observations and analysis of the starburst, PACS-819, at z=1.45
( M), using high-resolution (;
0.8 kpc) ALMA and multi-wavelength JWST images from the COSMOS-Web program.
Dissimilar to HST/ACS images in the rest-frame UV, the redder NIRCam and MIRI
images reveal a smooth central mass concentration and spiral-like features,
atypical for such an intense starburst. Through dynamical modeling of the CO
J=5--4 emission with ALMA, PACS-819 is rotation-dominated thus has a disk-like
nature. However, kinematic anomalies in CO and asymmetric features in the bluer
JWST bands (e.g., F150W) support a more disturbed nature likely due to
interactions. The JWST imaging further enables us to map the distribution of
stellar mass and dust attenuation, thus clarifying the relationships between
different structural components, not discernable in the previous HST images.
The CO J = 5 -- 4 and FIR dust continuum emission are co-spatial with a
heavily-obscured starbursting core (<1 kpc) which is partially surrounded by
much less obscured star-forming structures including a prominent arc, possibly
a tidally-distorted dwarf galaxy, and a clump, either a sign of an ongoing
violent disk instability or a recently accreted low-mass satellite. With
spatially-resolved maps, we find a high molecular gas fraction in the central
area reaching (/) and short depletion times
( 120 Myrs) across the entire system. These
observations provide insights into the complex nature of starbursts in the
distant universe and underscore the wealth of complementary information from
high-resolution observations with both ALMA and JWST.Comment: 18 pages, 12 figures, Submitted to Ap
An Ancient Massive Quiescent Galaxy Found in a Gas-rich z ∼ 3 Group
Deep Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope observations reveal the presence of a quenched massive galaxy within the z = 2.91 galaxy group RO-1001. With a mass-weighted stellar age of 1.6 ± 0.4 Gyr this galaxy is one of the oldest known at z ∼ 3, implying that most of its 1011 M⊙ of stars were rapidly formed at z > 6–8. This is a unique example of the predominantly passive evolution of a galaxy over at least 3 < z < 6 following its high-redshift quenching and a smoking-gun event pointing to the early imprint of an age–environment relation. At the same time, being in a dense group environment with extensive cold gas reservoirs as betrayed by a giant Lyα halo, the existence of this galaxy demonstrates that gas accretion shutdown is not necessary for quenching and its maintenance
Bulge formation inside quiescent lopsided stellar disks: connecting accretion, star formation and morphological transformation in a z ~ 3 galaxy group
We present well-resolved near-IR and sub-mm analysis of the three highly
star-forming massive () galaxies within the core of
the RO-1001 galaxy group at . Each of them displays kpc-scale
compact star-bursting cores with properties consistent with forming galaxy
bulges, embedded at the center of extended, massive stellar disks.
Surprisingly, the stellar disks are unambiguously both quiescent, and severely
lopsided. Therefore, `outside-in' quenching is ongoing in the three group
galaxies. We propose an overall scenario in which the strong mass lopsidedness
in the disks (ranging from factors of 1.6 to 3), likely generated under the
effects of accreted gas and clumps, is responsible for their star-formation
suppression, while funnelling gas into the nuclei and thus creating the central
starbursts. The lopsided side of the disks marks the location of accretion
streams impact, with additional matter components (dust and stars) detected in
their close proximity directly tracing the inflow direction. The interaction
with the accreted clumps, which can be regarded as minor-mergers, leads the
major axes of the three galaxies to be closely aligned with the outer
Lyman--emitting feeding filaments. These results provide the first
observational evidence of the impact of cold accretion streams on the formation
and evolution of the galaxies they feed. In the current phase, this is taking
the form of the rapid buildup of bulges under the effects of accretion, while
still preserving massive quiescent and lopsided stellar disks at least until
encountering a violent major-merger.Comment: Accepted for publication in A&