9 research outputs found
A Photon Burst Clears the Earliest Dusty Galaxies: Modelling Dust in High-redshift Galaxies from ALMA to JWST
The generation and evolution of dust in galaxies are important tracers for
star formation, and can characterize the rest-frame ultraviolet to infrared
emission from the galaxies. In particular understanding dust in high-redshift
galaxies are important for observational cosmology, as they would be necessary
to extract information on star formation in the early universe. We update the
public semi-analytical model A-SLOTH (Ancient Stars and Local Observables by
Tracing Halos) to model the evolution of dust, focusing on high-redshift
star-forming galaxies with stellar masses of --
observed by ALMA () and JWST (). We find that these
galaxies should qualitatively differ in their star formation properties; while
the samples in ALMA are explained by dust growth in normal star-forming
galaxies, the lack of dust in the samples by JWST requires dust ejection by
radiation pressure due to recent highly efficient star-formation within a few
10 Myr, with order 100 times higher efficiency than normal galaxies calibrated
by A-SLOTH. Depending on where the JWST galaxies locate on the luminosity
function, their bursty star formation histories inferred from our model can
have impacts for rates of star formation, supernova explosion, stellar
feedback, and detectability of dusty, mature galaxies in the very early
universe.Comment: 13 pages, 7 figures. Revised after MNRAS referee report. Comments
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The Supersonic Project: Star Formation in Early Star Clusters without Dark Matter
The formation mechanism of globular clusters (GCs) has long been debated by
astronomers. It was recently proposed that Supersonically Induced Gas Objects
(SIGOs), which formed in the early Universe due to the supersonic relative
motion of baryons and dark matter at recombination, could be the progenitors of
early globular clusters. In order to become GCs, SIGOs must form stars
relatively efficiently despite forming outside of dark matter halos. We
investigate the potential for star formation in SIGOs using cosmological
hydrodynamic simulations, including the aforementioned relative motions of
baryons and dark matter, molecular hydrogen cooling in primordial gas clouds,
and including explicit star formation. We find that SIGOs do form stars and
that the nascent star clusters formed through this process are accreted by dark
matter halos on short timescales (a few hundreds of Myr). Thus, SIGOs may be
found as intact substructures within these halos, analogous to many present-day
GCs. From this result, we conclude that SIGOs are capable of forming star
clusters with similar properties to globular clusters in the early Universe and
we discuss their detectablity by upcoming JWST surveys.Comment: 11 pages, 5 figure
The Supersonic Project: The eccentricity and rotational support of SIGOs and DM GHOSts
A supersonic relative velocity between dark matter (DM) and baryons (the
stream velocity) at the time of recombination induces the formation of low mass
objects with anomalous properties in the early Universe. We widen the scope of
the `Supersonic Project' paper series to include objects we term Dark Matter +
Gas Halos Offset by Streaming (DM GHOSts)--diffuse, DM-enriched structures
formed because of a physical offset between the centers of mass of DM and
baryonic overdensities. We present an updated numerical investigation of DM
GHOSts and Supersonically Induced Gas Objects (SIGOs), including the effects of
molecular cooling, in high resolution hydrodynamic simulations using the AREPO
code. Supplemented by an analytical understanding of their ellipsoidal
gravitational potentials, we study the population-level properties of these
objects, characterizing their morphology, spin, radial mass, and velocity
distributions in comparison to classical structures in non-streaming regions.
The stream velocity causes deviations from sphericity in both the gas and DM
components and lends greater rotational support to the gas. Low mass ( M) objects in regions of streaming demonstrate core-like
rotation and mass profiles. Anomalies in the rotation and morphology of DM
GHOSts could represent an early Universe analogue to observed ultra-faint dwarf
galaxies with variations in DM content and unusual rotation curves.Comment: 26 pages, 20 figure
The Supersonic Project: Lighting up the faint end of the JWST UV luminosity function
The James Webb Space Telescope (JWST) is capable of probing extremely early
eras of our Universe when the supersonic relative motions between dark matter
and baryonic overdensities modulate structure formation (). We study
low-mass galaxy formation including this "stream velocity" using high
resolution AREPO hydrodynamics simulations, and present theoretical predictions
of the UV luminosity function (UVLF) and galaxy stellar mass function (GSMF)
down to extremely faint and low mass galaxies (,
. We show that, although the stream velocity
suppresses early star formation overall, it induces a short period of rapid
star formation in some larger dwarfs, leading to an enhancement in the
faint-end of the UVLF at . We demonstrate that JWST observations are
close to this enhanced regime, and propose that the UVLF may constitute an
important probe of the stream velocity at high redshift for JWST and future
observatories.Comment: 12 pages, 7 figure
The Supersonic Project: Lighting Up the Faint End of the JWST UV Luminosity Function
The James Webb Space Telescope (JWST) is capable of probing extremely early eras of our Universe, when the supersonic relative motions between dark matter and baryonic overdensities modulate structure formation (z greater than or similar to 10). We study low-mass galaxy formation, including this "stream velocity," using high-resolution AREPO hydrodynamics simulations and present theoretical predictions of the UV luminosity function (UVLF) and galaxy stellar mass function down to extremely faint and low-mass galaxies (M UV greater than or similar to -15, 104 M circle dot <= M * <= 108 M circle dot). We show that, although the stream velocity suppresses early star formation overall, it induces a short period of rapid star formation in some larger dwarfs, leading to an enhancement in the faint end of the UVLF at z = 12. We demonstrate that JWST observations are close to this enhanced regime and propose that the UVLF may constitute an important probe of the stream velocity at high redshift for JWST and future observatories
Detections of [C II] 158 m and [O III] 88 m in a Local Lyman Continuum Emitter, Mrk 54, and its Implications to High-redshift ALMA Studies
We present integral field, far-infrared (FIR) spectroscopy of Mrk 54, a local
Lyman Continuum Emitter (LCE), obtained with FIFI-LS on the Stratospheric
Observatory for Infrared Astronomy. This is only the second time, after Haro
11, that [C II] 158 m and [O III] 88 m spectroscopy of the known LCEs
have been obtained. We find that Mrk 54 has a strong [C II] emission that
accounts for % of the total FIR luminosity, whereas it has only moderate
[O III] emission, resulting in the low [O III]/[C II] luminosity ratio of
. In order to investigate whether [O III]/[C II] is a useful
tracer of (LyC escape fraction), we examine the correlations of
[O III]/[C II] and (i) the optical line ratio of [O III]
5007 \AA/[O II] 3727 \AA, (ii) specific star formation rate, (iii) [O III] 88
m/[O I] 63 m ratio, (iv) gas phase metallicity, and (v) dust
temperature based on a combined sample of Mrk 54 and the literature data from
the Herschel Dwarf Galaxy Survey and the LITTLE THINGS Survey. We find that
galaxies with high [O III]/[C II] luminosity ratios could be the result of high
ionization (traced by ), bursty star formation, high
ionized-to-neutral gas volume filling factors (traced by [O III] 88 m/[O
I] 63 m), and low gas-phase metallicities, which is in agreement with
theoretical predictions. We present an empirical relation between the [O
III]/[C II] ratio and based on the combination of the [O III]/[C
II] and correlation, and the known relation between
and . The relation implies that high-redshift galaxies with high
[O III]/[C II] ratios revealed by ALMA may have ,
significantly contributing to the cosmic reionization.Comment: 14 pages, 5 figures, Accepted for publication in Ap
The Supersonic Project: The Early Evolutionary Path of Supersonically Induced Gas Objects
Supersonically induced gas objects (SIGOs) are a class of early universe objects that have gained attention as a potential formation route for globular clusters. SIGOs have recently begun to be studied in the context of molecular hydrogen cooling, which is key to characterizing their structure and evolution. Studying the population-level properties of SIGOs with molecular cooling is important for understanding their potential for collapse and star formation, and for addressing whether SIGOs can survive to the present epoch. Here, we investigate the evolution of SIGOs before they form stars, using a combination of numerical and analytical analysis. We study timescales important to the evolution of SIGOs at a population level in the presence of molecular cooling. Revising the previous formulation for the critical density of collapse for SIGOs allows us to show that their prolateness tends to act as an inhibiting factor to collapse. We find that simulated SIGOs are limited by artificial two-body relaxation effects that tend to disperse them. We expect that SIGOs in nature will be longer lived compared to our simulations. Further, the fall-back timescale on which SIGOs fall into nearby dark matter halos, potentially producing a globular-cluster-like system, is frequently longer than their cooling timescale and the collapse timescale on which they shrink through gravity. Therefore, some SIGOs have time to cool and collapse outside of halos despite initially failing to exceed the critical density. From this analysis we conclude that SIGOs should form stars outside of halos in nonnegligible stream velocity patches in the universe
The Supersonic Project: Star Formation in Early Star Clusters without Dark Matter
The formation mechanism of globular clusters (GCs) has long been debated by astronomers. It was recently proposed that supersonically induced gas objects (SIGOs)–which formed in the early Universe due to the supersonic relative motion of baryons and dark matter at recombination–could be the progenitors of early GCs. In order to become GCs, SIGOs must form stars relatively efficiently despite forming outside of dark matter halos. We investigate the potential for star formation in SIGOs using cosmological hydrodynamic simulations, including the aforementioned relative motions of baryons and dark matter, molecular hydrogen cooling in primordial gas clouds, and explicit star formation. We find that SIGOs do form stars and that the nascent star clusters formed through this process are accreted by dark matter halos on short timescales (∼a few hundred megayears). Thus, SIGOs may be found as intact substructures within these halos, analogous to many present-day GCs. From this result, we conclude that SIGOs are capable of forming star clusters with similar properties to globular clusters in the early Universe, and we discuss their detectability by upcoming JWST surveys
RIOJA I. The core of the highest redshift galaxy overdensity at confirmed by NIRSpec/JWST
The proto-clusters in the epoch of reionization, traced by galaxies
overdensity regions, are ideal laboratories to study the process of stellar
assembly and cosmic reionization. We present the spectroscopic confirmation of
the core of the most distant proto-cluster at , A2744-z7p9OD, with
the James Webb Space Telescope NIRSpec integral field unit spectroscopy. The
core region includes as many as 4 galaxies detected in [O III] 4960 A and 5008
A in a small area of , corresponding to 11 kpc
11 kpc. Three member galaxies are also tentatively detected in dust
continuum in ALMA Band 6, which is consistent with their red ultraviolet
continuum slopes, . The member galaxies have stellar masses in
the range of log() and star formation rates
of yr, showing a diversity in their
properties. FirstLight cosmological simulations reproduce the physical
properties of the member galaxies including the stellar mass, [OIII]
luminosity, and dust-to-stellar mass ratio, and predict that the member
galaxies are on the verge of merging in a few to several tens Myr to become a
large galaxy with . The presence of
a multiple merger and evolved galaxies in the core region of A2744-z7p9OD
indicates that environmental effects are already at work 650 Myr after the Big
Bang.Comment: 10 pages, 4 figures, 1 table, submitted to ApJ