Abstract
We investigate the blue and optical rest-frame sizes (
λ
≃ 2300–4000 Å) of three compact star-forming regions in a galaxy at
z
= 4 strongly lensed (×30, ×45, and ×100) by the Hubble Frontier ...Field galaxy cluster A2744 using GLASS-ERS James Webb Space Telescope (JWST)/NIRISS imaging at 1.15
μ
m, 1.50
μ
m, and 2.0
μ
m with a point-spread function ≲0.″1. In particular, the Balmer break is probed in detail for all multiply imaged sources of the system. With ages of a few tens of Myr, stellar masses in the range (0.7–4.0) ×10
6
M
⊙
and optical/ultraviolet effective radii spanning the interval 3 <
R
eff
< 20 pc, such objects are currently the highest-redshift (spectroscopically confirmed) gravitationally bound young massive star clusters (YMCs), with stellar mass surface densities resembling those of local globular clusters. Optical (4000 Å, JWST-based) and ultraviolet (1600 Å, Hubble Space Telescope–based) sizes are fully compatible. The contribution to the ultraviolet underlying continuum emission (1600 Å) is ∼30%, which decreases by a factor of 2 in the optical for two of the YMCs (∼4000 Å rest-frame), reflecting the young ages (<30 Myr) inferred from the spectral energy distribution fitting and supported by the presence of high-ionization lines secured with the Very Large Telescope/MUSE. Such bursty forming regions enhance the specific star formation rate of the galaxy, which is ≃10 Gyr
−1
. This galaxy would be among the extreme analogs observed in the local universe having a high star formation rate surface density and a high occurrence of massive stellar clusters in formation.
The escape fraction of Lyman-continuum (LyC) photons (
f
esc
) is a key parameter for determining the sources of cosmic reionization at
z
≥ 6. At these redshifts, owing to the opacity of the ...intergalactic medium, the LyC emission cannot be measured directly. However, LyC leakers during the epoch of reionization could be identified using indirect indicators that have been extensively tested at low and intermediate redshifts. These include a high O
III
/O
II
flux ratio, high star-formation surface density, and compact sizes. In this work, we present observations of 29 4.5 ≤
z
≤ 8 gravitationally lensed galaxies in the Abell 2744 cluster field. From a combined analysis of JWST-NIRSpec and NIRCam data, we accurately derived their physical and spectroscopic properties: our galaxies have low masses (log(
M
⋆
)∼8.5), blue UV spectral slopes (
β
∼ −2.1), compact sizes (
r
e
∼ 0.3 − 0.5 kpc), and high O
III
/O
II
flux ratios. We confirm that these properties are similar to those characterizing low-redshift LyC leakers. Indirectly inferring the fraction of escaping ionizing photons, we find that more than 80% of our galaxies have predicted
f
esc
values larger than 0.05, indicating that they would be considered leakers. The average predicted
f
esc
value of our sample is 0.12, suggesting that similar galaxies at
z
≥ 6 have provided a substantial contribution to cosmic reionization.
ABSTRACT
We use VANDELS spectroscopic data overlapping with the ≃7 Ms Chandra Deep Field South survey to extend studies of high-mass X-ray binary systems (HMXBs) in 301 normal star-forming galaxies ...in the redshift range 3 < z < 5.5. Our analysis evaluates correlations between X-ray luminosities (LX), star formation rates (SFRs), and stellar metallicities (Z⋆) to higher redshifts and over a wider range in galaxy properties than hitherto. Using a stacking analysis performed in bins of both redshift and SFR for sources with robust spectroscopic redshifts without AGN signatures, we find convincing evolutionary trends in the ratio LX/SFR to the highest redshifts probed, with a stronger trend for galaxies with lower SFRs. Combining our data with published samples at lower redshift, the evolution of LX/SFR to z ≃ 5 proceeds as (1 + z)1.03 ± 0.02. Using stellar metallicities derived from photospheric absorption features in our spectroscopic data, we confirm indications at lower redshifts that LX/SFR is stronger for metal-poor galaxies. We use semi-analytic models to show that metallicity dependence of LX/SFR alone may not be sufficient to fully explain the observed redshift evolution of X-ray emission from HMXBs, particularly for galaxies with SFR < 30 M⊙ yr−1. We speculate that reduced overall stellar ages and ‘burstier’ star formation histories in the early Universe may lead to higher LX/SFR for the same metallicity. We then define the redshift-dependent contribution of HMXBs to the integrated X-ray luminosity density and, in comparison with models, find that the contribution of HMXBs to the cosmic X-ray background at z > 6 may be ≳0.25 dex higher than previously estimated.
The Epoch of Reionization (EoR) began when galaxies grew in abundance and luminosity, so their escaping Lyman continuum (LyC) radiation started ionizing the surrounding neutral intergalactic medium ...(IGM). Despite significant recent progress, the nature and role of cosmic reionizers are still unclear: in order to define them, it would be necessary to directly measure their LyC escape fraction (
f
esc
). However, this is impossible during the EoR due to the opacity of the IGM. Consequently, many efforts at low and intermediate redshift have been made to determine measurable indirect indicators in high-redshift galaxies so that their
f
esc
can be predicted. This work presents the analysis of the indirect indicators of 62 spectroscopically confirmed star-forming galaxies at 6 ≤
z
≤ 9 from the Cosmic Evolution Early Release Science (CEERS) survey, combined with 12 sources with public data from other JWST-ERS campaigns. From the NIRCam and NIRSpec observations, we measured their physical and spectroscopic properties. We discovered that on average 6 <
z
< 9 star-forming galaxies are compact in the rest-frame UV (
r
e
∼ 0.4 kpc), are blue sources (UV-
β
slope ∼ − 2.17), and have a predicted
f
esc
of about 0.13. A comparison of our results to models and predictions as well as an estimation of the ionizing budget suggests that low-mass galaxies with UV magnitudes fainter than
M
1500
= −18 that we currently do not characterize with JWST observations probably played a key role in the process of reionization.
The resonant scattering interaction between Ly α photons and neutral hydrogen implies that a partially neutral intergalactic medium has the ability to significantly impact the detectability of Ly α ...emission in galaxies. Thus, the redshift evolution of the Ly α equivalent width distribution of galaxies offers a key observational probe of the degree of ionization during the Epoch of Reionization (EoR). Previous in-depth investigations at z ≥ 7 were limited by ground-based instrument capabilities. We present an extensive study of the evolution of Ly α emission from galaxies at 4.5 < z < 8.5, observed as part of the CEERS and JADES surveys in the JWST NIRSpec/PRISM configuration. The sample consists of 235 galaxies in the redshift range of 4.1 < z < 9.9. We identified 65 of them as Ly α emitters. We first measured the Ly α escape fractions from Ly α to Balmer line flux ratios and explored the correlations with the inferred galaxies’ physical properties, which are similar to those found at lower redshift. We also investigated the possible connection between the escape of Ly α photons and the inferred escape fractions of LyC photons obtained from indirect indicators, finding no secure correlation. We then analyzed the redshift evolution of the Ly α emitter fraction, finding lower average values at z = 5 and 6 compared to previous ground-based observations. At z = 7, the GOODS-S results are aligned with previous findings, whereas the visibility in the EGS field appears to be enhanced. This discrepancy in Ly α visibility between the two fields could potentially be attributed to the presence of early reionized regions in the EGS. Such a broad variance is also expected in the Cosmic Dawn II radiation-hydrodynamical simulation. The average Ly α emitter fraction obtained from the CEERS+JADES data continues to increase from z = 5 to 7, ultimately declining at z = 8. This suggests a scenario in which the ending phase of the EoR is characterized by ∼1 pMpc ionized bubbles around a high fraction of moderately bright galaxies. Finally, we characterize such two ionized regions found in the EGS at z = 7.18 and z = 7.49 by estimating the radius of the ionized bubble that each of the spectroscopically-confirmed members could have created.
Context.
Feedback from massive stars plays a crucial role in regulating the growth of young star-forming galaxies (SFGs) and in shaping their interstellar medium (ISM). This feedback contributes to ...the removal and mixing of metals via galactic outflows and to the clearance of neutral gas, which facilitates the escape of ionizing photons.
Aims.
Our goal is to study the impact of stellar feedback on the chemical abundances of the ISM in a sample of SFGs with strong emission lines at
z
∼ 3.
Methods.
We selected 35 low-mass SFGs (7.9 < log(
M
⋆
/
M
⊙
) < 10.3) from deep spectroscopic surveys based on their CIII
λ
1908 emission. We used new follow-up near-infrared (NIR) observations to examine their rest-optical emission lines and to identify ionized outflow signatures through broad emission line wings detected after Gaussian modeling of OIII
λλ
4959,5007 profiles. We characterized the gas-phase metallicity and carbon-to-oxygen (C/O) abundance of the galaxies using a
T
e
-based method via the OIII
λ
1666/OIII
λ
5007 ratio and photoionization models.
Results.
We find line ratios and rest-frame equivalent widths (EWs) characteristic of high-ionization conditions powered by massive stars. Our sample displays a mean rest-frame EW(OIII
λ
5007) of ∼560 Å, while about 15% of the SFGs show EW(OIII
λλ
4959,5007) > 1000 Å and EW(CIII) > 5 Å, closely resembling those now seen in epoch of reionization (EoR) galaxies with the
James Webb
Space Telescope. We find high
T
e
values, which imply low gas-phase metallicities 12+log(O/H) ∼ 7.5–8.5 (mean of 17% solar) and C/O abundances from 23% to 128% solar, with no apparent increasing trend with metallicity. Our sample follows the mass-metallicity relation at
z
∼ 3, with some galaxies showing lower gas-phase metallicities. This results in significant deviations from the fundamental metallicity relation. From our OIII
λλ
4959,5007 line profile modeling, we find that 65% of our sample shows an outflow component, which is found both blue- or redshifted relative to the ionized gas systemic velocity, and the mean maximum velocities are
v
max
∼ 280 km s
−1
. We find a weak correlation between
v
max
and the star formation rate surface density (Σ
SFR
) of
v
max
= (2.41 ± 0.03) × Σ
SFR
(0.06 ± 0.03)
. Moreover, we find that the mass-loading factor
μ
of our galaxy sample is typically lower than in more massive galaxies from the literature, but it is higher than in typical local dwarf galaxies. In the stellar mass range covered by our sample, we find that
μ
increases with Σ
SFR
. This suggests that for a given stellar mass, denser starbursts in low-mass galaxies produce stronger outflows. Our results complement the picture drawn by similar studies at lower redshift, suggesting that the removal of ionized gas in low-mass SFGs driven by stellar feedback is regulated by their stellar mass and by the strength and concentration of their star formation, that is, Σ
SFR
.
Osteoporosis (OMIM166710) is a common skeletal disorder characterized by low bone mass and microarchitectural deterioration of bone tissue with increased susceptibility to fracture. Osteoporosis has ...a complex etiology and is considered a multifactorial polygenic disease in which genetic determinants are modulated by hormonal, environmental, and nutritional factors. Estrogens are known to play an important role in regulating bone homeostasis and preventing postmenopausal bone loss. They act through binding to two different estrogen receptors (ERs), ERα (OMIM133430) and ERβ (OMIM601663), which are members of the nuclear receptor superfamily of ligand-activated transcription factors. Different polymorphisms have been described in both the ER α and ER β genes. Although a large number of association studies have been performed, the individual contribution of these polymorphisms to the pathogenesis of osteoporosis remains to be universally confirmed. Moreover, an important aim in future work will be to define their functional molecular consequences and their interaction with the environment in the causation of the osteoporotic phenotype. A further promising application of these polymorphisms comes from their pharmacogenomic implications, with the possibility of providing better guidance for therapeutic regimens, such as estrogen replacement therapy and selective ER modulators. At the moment, no recommendations for population-based screening can be made.
Aims.
We investigate the ionizing properties of the pair of bright Ly
α
emitting galaxies BDF521 and BDF2195 at
z
= 7.012 in order to constrain their contribution to the formation of the Bremer Deep ...Field (BDF) ‘reionized bubble’ in which they have been shown to reside.
Methods.
We obtain constraints on four UV emission lines (the CIV
λ
1548 doublet, HeII
λ
1640, the OIII
λ
1660 doublet, and the CIII
λ
1909 doublet) from deep VLT X-shooter observations and compare them to those available for other high-redshift objects, and to models with mixed stellar and active galactic nucleus (AGN) emission. We use this spectroscopic information, together with the photometry available in the field, to constrain the physical properties of the two objects using the spectro-photometric fitting code BEAGLE.
Results.
We do not detect any significant emission at the expected position of the UV lines, with 3
σ
upper limits of equivalent width (EW) ≲2–7 Å rest-frame. We find that the two objects have a lower CIII emission than expected on the basis of the correlation between the Ly
α
and CIII EWs. The EW limits on CIV and HeII emission exclude pure AGN templates at ∼2 − 3
σ
significance, and only models with a ≲40% AGN contribution are compatible with the observations. The two objects are found to be relatively young (∼20–30 Myrs) and metal-poor (≲0.3
Z
⊙
), with stellar masses of a few 10
9
M
⊙
. Their production rate of hydrogen ionizing photons per intrinsic UV luminosity is log(
ξ
ion
*
/Hz erg
−1
) = 25.02–25.26, consistent with values typically found in high-redshift galaxies, but more than twice lower than values measured in
z
> 7 galaxies with strong CIII and/or optical line emission (≃25.6–25.7).
Conclusions.
The two BDF emitters show no evidence of higher-than-average ionizing capabilities and are not capable of reionizing their surroundings by their own means, under realistic assumptions of the escape fraction of ionizing photons. Therefore, a dominant contribution to the formation of the reionized bubble must have been provided by fainter companion galaxies. The capabilities of the
James Webb
Space Telescope will be needed for spectroscopic confirmation of these objects.
VANDELS is a deep spectroscopic survey, performed with the VIMOS instrument at VLT, aimed at studying in detail the physical properties of high-redshift galaxies. VANDELS targeted ~2100 sources at 1 ...<
z <
6.5 in the CANDELS
Chandra
Deep-Field South (CDFS) and Ultra-Deep Survey (UDS) fields. In this paper, we present the public release of the spectroscopic measurement catalogues from this survey, featuring emission and absorption line centroids, fluxes, and rest-frame equivalent widths obtained through a Gaussian fit, as well as a number of atomic and molecular indices (e.g. Lick) and continuum breaks (e.g. D4000), and including a correction to be applied to the error spectra. We describe the measurement methods and the validation of the codes that were used.
The 700 ks Chandra Spiderweb Field Tozzi, P.; Pentericci, L.; Gilli, R. ...
Astronomy and astrophysics (Berlin),
06/2022, Letnik:
662
Journal Article
Recenzirano
Aims.
We present an analysis of the 700 ks
Chandra
ACIS-S observation of the field around the radio galaxy J1140-2629 (the Spiderweb Galaxy) at
z
= 2.156, focusing on the nuclear activity in the ...associated large-scale environment.
Methods.
We identified unresolved X-ray sources in the field down to flux limits of 1.3 × 10
−16
and 3.9 × 10
−16
erg s
−1
cm
−2
in the soft (0.5–2.0 keV) and hard (2–10 keV) band, respectively. We searched for counterparts in the optical, near-infrared, and submillimeter catalogs available in the literature to identify X-ray sources belonging to the protocluster and derived their X-ray properties.
Results.
We detect 107 X-ray unresolved sources within 5 arcmin (corresponding to 2.5 Mpc) of J1140-2629, among which 13 have optical counterparts with spectroscopic redshift 2.11 <
z
< 2.20, and 1 source has a photometric redshift consistent with this range. The X-ray-emitting protocluster members are distributed approximately over a ∼3.2 × 1.3 Mpc
2
rectangular region. An X-ray spectral analysis for all the sources within the protocluster shows that their intrinsic spectral slope is consistent with an average ⟨Γ⟩∼1.84 ± 0.04. Excluding the Spiderweb Galaxy, the best-fit intrinsic absorption for five protocluster X-ray members is
N
H
> 10
23
cm
−2
, while another six have upper limits of the order of a few times 10
22
cm
−2
. Two sources can only be fitted with very flat Γ ≤ 1, and are therefore considered Compton-thick candidates. The 0.5–10 keV rest-frame luminosities of the 11 Compton-thin protocluster members corrected for intrinsic absorption are greater than 2 × 10
43
erg s
−1
. These values are typical for the bright end of a Seyfert-like distribution and significantly greater than X-ray luminosities expected from star formation activity. The X-ray luminosity function of the AGN in the volume associated to the Spiderweb protocluster in the range 10
43
<
L
X
< 10
44.5
erg s
−1
is at least ten times higher than that in the field at the same redshift and significantly flatter, implying an increasing excess at the bright end. The X-ray AGN fraction is measured to be 25.5 ± 4.5% of the spectroscopically confirmed members in the stellar mass range log(
M
*
/
M
⊙
) > 10.5. This value corresponds to an enhancement factor of 6.0
−3.0
+9.0
for the nuclear activity with
L
0.5 − 10 keV
> 4 × 10
43
erg s
−1
with respect to the COSMOS field at comparable redshifts and stellar mass range.
Conclusions.
We conclude that the galaxy population in the Spiderweb protocluster is characterized by enhanced X-ray nuclear activity triggered by environmental effects on megaparsec scales.
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