ABSTRACT
A wealth of extragalactic populations completely missed at UV-optical wavelengths has been identified in the last decade, combining the deepest HST and Spitzer observations. These dark ...sources are thought to be dusty and star-forming systems at 3 < z < 5, and major contributors to the stellar mass build up. In this letter, we report an investigation of the deep JWST survey in the SMACS0723 cluster, analysing NIRCam and MIRI images. We search for sources in the F444W band that are undetected in the F200W catalogues. We characterize the properties of these sources via detailed Spectral Energy Distribution (SED) modelling, accounting for a wide set of parameters and star formation histories, after a careful determination of their photometry. Among a robust sample of 20 candidates, we identify a mixed population of very red sources. We highlight the identification of evolved systems, with stellar masses M* ∼ 109–11 M⊙ at 8 < z < 13 characterized by unexpectedly important dust content at those epochs (AV up to ∼5.8 mag), challenging current model predictions. We further identify an extremely red source (F200W-F440W ∼ 7 mag) that can be reproduced only by the spectrum of a passive, quenched galaxy of M* ∼ 1011.56 M⊙ at z ∼ 5, filled of dust (AV ∼ 5 mag).
Abstract
Galaxy evolution can be dramatically affected by the environment, especially by the dense environment of a galaxy cluster. Recent observational studies show that massive galaxies undergoing ...strong ram-pressure stripping (RPS) have an enhanced frequency of nuclear activity. We investigate this topic using a suite of wind-tunnel hydrodynamical simulations of a massive
M
star
= 10
11
M
⊙
disk galaxy with 39 pc resolution and including star formation and stellar feedback. We find that RPS increases the inflow of gas to the galaxy center regardless of the wind impact angle. This increase is driven by the mixing of interstellar and nonrotating intracluster media at all wind angles, and by increased torque on the inner disk gas, mainly from local pressure gradients when the intracluster medium (ICM) wind has an edge-on component. In turn, the strong pressure torques are driven by rising ram pressure. We estimate the black hole (BH) accretion using Bondi–Hoyle and torque models, and compare it with the mass flux in the central 140 pc region. We find that the torque model predicts much less accretion onto the BH of a RPS galaxy than the Bondi–Hoyle estimator. We argue that both models are incomplete: the commonly used torque model does not account for torques caused by the gas distribution or local pressure gradients, while the Bondi–Hoyle estimator depends on the sound speed of the hot gas, which includes the ICM in stripped galaxies. An estimator that accounts for this missing physics is required to capture BH accretion in a RPS galaxy.
We study the gas kinematics traced by the 21 cm emission of a sample of six H i-rich low surface brightness galaxies classified as ultra-diffuse galaxies (UDGs). Using the 3D kinematic modeling code ...3DBarolo we derive robust circular velocities, revealing a startling feature: H i-rich UDGs are clear outliers from the baryonic Tully-Fisher relation, with circular velocities much lower than galaxies with similar baryonic mass. Notably, the baryon fraction of our UDG sample is consistent with the cosmological value: these UDGs are compatible with having no "missing baryons" within their virial radii. Moreover, the gravitational potential provided by the baryons is sufficient to account for the amplitude of the rotation curve out to the outermost measured point, contrary to other galaxies with similar circular velocities. We speculate that any formation scenario for these objects will require very inefficient feedback and a broad diversity in their inner dark matter content.
Abstract
Ram pressure stripping of satellite galaxies is thought to be a ubiquitous process in galaxy clusters, and a growing number of observations reveal satellites at different stages of ...stripping. However, in order to determine the fate of any individual galaxy, we turn to predictions from either simulations or analytic models. It is not well determined whether simulations and analytic models agree in their predictions, nor the causes of disagreement. Here we investigate ram pressure stripping in the reference EAGLE hydrodynamical cosmological simulation, and compare the results to predictions from analytic models. We track the evolution of galaxies with stellar mass
M
*
> 10
9
M
⊙
and initial bound gas mass
M
gas
> 10
9
M
⊙
that fall into galaxy clusters (
M
200
c
> 10
14
M
⊙
) between
z
= 0.27 and
z
= 0. We divide each galaxy into its neutral gas disk and hot ionized gas halo and compare the evolution of the stripped gas fraction in the simulation to that predicted by analytic formulations for the two gas phases, as well as to a toy model that computes the motions of gas particles under the combined effects of gravity and a spatially uniform ram pressure. We find that the analytic models generally underpredict the stripping rate of neutral gas and overpredict that of ionized gas, with significant scatter between the model and simulation stripping timescales. This is due to opposing physical effects: the enhancement of ram pressure stripping by stellar feedback, and the suppression of stripping by the compaction of galactic gas.
Abstract
Growing evidence in support of a connection between active galactic nuclei (AGN) activity and the ram pressure stripping (RPS) phenomenon has been found both observationally and ...theoretically in the past decades. In this work, we further explore the impact of RPS on the AGN activity by estimating the gas-phase metallicity of nuclear regions and the mass–metallicity relation of galaxies at
z
≤ 0.07 and with stellar masses
log
M
*
/
M
⊙
≥
9.0
, either experiencing RPS or not. To measure oxygen abundances, we exploit Integral Field Spectroscopy data from the GASP and MaNGA surveys, photoionization models generated with the code
Cloudy
and the code
Nebulabayes
to compare models and observations. In particular, we build
Cloudy
models to reproduce line ratios induced by photoionization from stars, AGN, or a contribution of both. We find that the distributions of metallicity and O
iii
λ
5007 luminosity of galaxies undergoing RPS are similar to the ones of undisturbed galaxies. Independently of the RPS, we do not find a correlation between stellar mass and AGN metallicity in the mass range
log
M
*
/
M
⊙
≥
10.4
, while for the star-forming galaxies we observe the well-known mass–metallicity relation between
9.0
≤
log
M
*
/
M
⊙
≤
10.8
with a scatter mainly driven by the star formation rate and a plateau around
log
M
*
/
M
⊙
∼
10.5
. The gas-phase metallicity in the nuclei of AGN hosts is enhanced with respect to those of star-forming galaxies by a factor of ∼ 0.05 dex regardless of the RPS.
ABSTRACT
We study the gas kinematics of a sample of six isolated gas-rich low surface brightness galaxies, of the class called ultra-diffuse galaxies (UDGs). These galaxies have recently been shown ...to be outliers from the baryonic Tully–Fisher relation (BTFR), as they rotate much slower than expected given their baryonic mass, and to have a baryon fraction similar to the cosmological mean. By means of a 3D kinematic modelling fitting technique, we show that the H i in our UDGs is distributed in ‘thin’ regularly rotating discs and we determine their rotation velocity and gas velocity dispersion. We revisit the BTFR adding galaxies from other studies. We find a previously unknown trend between the deviation from the BTFR and the exponential disc scale length valid for dwarf galaxies with circular speeds ≲ 45 km s−1, with our UDGs being at the extreme end. Based on our findings, we suggest that the high baryon fractions of our UDGs may originate due to the fact that they have experienced weak stellar feedback, likely due to their low star formation rate surface densities, and as a result they did not eject significant amounts of gas out of their discs. At the same time, we find indications that our UDGs may have higher-than-average stellar specific angular momentum, which can explain their large optical scale lengths.
Abstract
Cluster galaxies are subject to the ram pressure exerted by the intracluster medium, which can perturb or even strip away their gas while leaving the stars undisturbed. We model the ...distribution and kinematics of the stars and the molecular gas in four late-type cluster galaxies (JO201, JO204, JO206, and JW100), which show tails of atomic and ionized gas indicative of ongoing ram pressure stripping. We analyze MUSE@VLT data and CO data from the Atacama Large Millimeter Array searching for signatures of radial gas flows, ram pressure stripping, and other perturbations. We find that all galaxies, with the possible exception of JW100, host stellar bars. Signatures of ram pressure are found in JO201 and JO206, which also shows clear indications of ongoing stripping in the molecular disk outskirts. The stripping affects the whole molecular gas disk of JW100. The molecular gas kinematics in JO204 is instead dominated by rotation rather than ram pressure. We also find indications of enhanced turbulence of the molecular gas compared to field galaxies. Large-scale radial flows of molecular gas are present in JO204 and JW100, but more uncertain in JO201 and JO206. We show that our sample follows the molecular gas mass–size relation, confirming that it is essentially independent of environment even for the most extreme cases of stripping. Our findings are consistent with the molecular gas being affected by the ram pressure on different timescales and less severely than the atomic and ionized gas phases, likely because the molecular gas is denser and more gravitationally bound to the galaxy.
Abstract
We report the serendipitous discovery of an unprecedented interaction between the radio lobe of a radio galaxy and a spiral galaxy. The discovery was made thanks to LOFAR observations at 144 ...MHz of the galaxy cluster A160 (
z
= 0.04317) provided by the LOFAR Two-metre Sky Survey. The new low-frequency observations revealed that one of the radio plumes of the central galaxy GIN 049 overlaps the spiral galaxy JO36. Previous studies carried out with MUSE revealed that the warm ionized gas in the disk of JO36, traced by the H
α
emission, is severely truncated with respect to the stellar disk. We further explore this unique system by including new uGMRT observations at 675 MHz to map the spectral index. The emerging scenario is that JO36 has interacted with the radio plume in the past 200–500 Myr. The encounter resulted in a positive feedback event for JO36 in the form of a star formation rate burst of ∼14
M
⊙
yr
−1
. In turn, the galaxy passage left a trace in the radio-old plasma by reshaping the old relativistic plasma via magnetic draping.
It is commonly believed that galaxies use, throughout Hubble time, a very small fraction of the baryons associated with their dark matter halos to form stars. This so-called low star formation ...efficiency f⋆ ≡ M⋆/fbMhalo, where fb ≡ Ωb/Ωc is the cosmological baryon fraction, is expected to reach its peak at nearly L* (at efficiency ≈20%) and decline steeply at lower and higher masses. We have tested this using a sample of nearby star-forming galaxies, from dwarfs (M⋆ ≃ 107 M⊙) to high-mass spirals (M⋆ ≃ 1011 M⊙) with HI rotation curves and 3.6 μm photometry. We fit the observed rotation curves with a Bayesian approach by varying three parameters, stellar mass-to-light ratio Υ⋆, halo concentration c, and mass Mhalo. We found two surprising results: (1) the star formation efficiency is a monotonically increasing function of M⋆ with no sign of a decline at high masses, and (2) the most massive spirals (M⋆ ≃ 1−3 × 1011 M⊙) have f⋆ ≈ 0.3−1, i.e. they have turned nearly all the baryons associated with their halos into stars. These results imply that the most efficient galaxies at forming stars are massive spirals (not L* galaxies); they reach nearly 100% efficiency, and thus once both their cold and hot gas is considered in the baryon budget, they have virtually no missing baryons. Moreover, there is no evidence of mass quenching of the star formation occurring in galaxies up to halo masses of a few × 1012 M⊙.
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