64 research outputs found
Prospects for Observing the low-density Cosmic Web in Lyman-alpha Emission
Mapping the intergalactic medium (IGM) in Lyman- emission would yield
unprecedented tomographic information on the large-scale distribution of
baryons and potentially provide new constraints on the UV background and
various feedback processes relevant to galaxy formation. Here, we use a
cosmological hydrodynamical simulation to examine the Lyman- emission
of the IGM due to collisional excitations and recombinations in the presence of
a UV background. We focus on gas in large-scale-structure filaments in which
Lyman- radiative transfer effects are expected to be moderate. At low
density the emission is primarily due to fluorescent re-emission of the
ionising UV background due to recombinations, while collisional excitations
dominate at higher densities. We discuss prospects of current and future
observational facilities to detect this emission and find that the emission of
filaments of the cosmic web will typically be dominated by the halos and
galaxies embedded in them, rather than by the lower density filament gas
outside halos. Detecting filament gas directly would require a very long
exposure with a MUSE-like instrument on the ELT. Our most robust predictions
that act as lower limits indicate this would be slightly less challenging at
lower redshifts (). We also find that there is a large amount of
variance between fields in our mock observations. High-redshift protoclusters
appear to be the most promising environment to observe the filamentary IGM in
Lyman- emission.Comment: 20 pages, 13 figures. Accepted for publication in Astronomy &
Astrophysics. Accepted version contains several revisions following
suggestions made in the review proces
Spatially resolved Kennicutt-Schmidt relation at z ≈ 7 and its connection with the interstellar medium properties
We exploit moderately resolved [O III], [C II] and dust continuum ALMA observations to derive the gas density (n), the gas-phase metallicity (Z) and the deviation from the Kennicutt-Schmidt (KS) relation (κs) on ≈sub−kpc
scales in the interstellar medium (ISM) of five bright Lyman Break Galaxies at the Epoch of Reionization (z ≈ 7). To do so, we use GLAM, a state-of-art, physically motivated Bayesian model that links the [C II]and [O III] surface brightness (Σ[CII], Σ[OIII]) and the SFR surface density (ΣSFR) to n, κs, and Z. All five sources are characterized by a central starbursting region, where the Σgas vs ΣSFR align ≈10 × above the KS relation (κs ≈ 10). This translates into gas depletion times in the range tdep ≈ 80 − 250 Myr. The inner starbursting centers are characterized by higher gas density (log (n/cm−3) ≈ 2.5 − 3.0) and higher metallicity (log (Z/Z⊙) ≈ −0.5) than the galaxy outskirts. We derive marginally negative radial metallicity gradients (∇log Z ≈ −0.03 ± 0.07 dex/kpc), and a dust temperature (Td ≈ 32 − 38 K) that anticorrelates with the gas depletion time
Dual constraints with ALMA: new [O III] 88 m and dust-continuum observations reveal the ISM conditions of luminous LBGs at
We present new [O III] 88 m observations of five bright
Lyman-break galaxies spectroscopically confirmed by ALMA through the [C II] 158
m line, unlike recent [O III] detections where Lyman-
was used. This nearly doubles the sample of Epoch of Reionisation galaxies with
robust () detections of [C II] and [O III]. We perform a
multi-wavelength comparison with new deep HST images of the rest-frame UV,
whose compact morphology aligns well with [O III] tracing ionised gas. By
contrast, we find more spatially extended [C II] emission likely produced in
neutral gas, as indicated by a [N II] 205 m non-detection in one
source. We find a positive correlation between the equivalent width of the
optical [O III] and H lines and the [O III]/[C II] ratio, as seen
in local metal-poor dwarf galaxies. Cloudy models of a nebula of typical
density harbouring a young stellar population with a high ionisation parameter
appear to adequately reproduce the far-infrared lines. Surprisingly, however,
our models fail to reproduce the strength of [O III] 88 m, unless we
assume an /Fe enhancement and a near-solar nebular oxygen
abundance. On spatially resolved scales, we find [O III]/[C II] shows a
tentative anti-correlation with infrared excess, , also
seen on global scales in the local Universe. Finally, we introduce the
far-infrared spectral energy distribution fitting code MERCURIUS to show that
dust-continuum measurements of one source appear to favour a low dust
temperature coupled with a high dust mass. This implies a high stellar
metallicity yield and may point towards the need of dust production or
grain-growth mechanisms beyond supernovae.Comment: 23 pages, 11 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
First insights into the ISM at z > 8 with JWST: possible physical implications of a high [O III] λ4363/[O III] λ5007
© 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We present a detailed analysis of the rest-frame optical emission line ratios for three spectroscopically confirmed galaxies at z > 7.5. The galaxies were identified in the James Webb Space Telescope (JWST) Early Release Observations field SMACS J0723.3 − 7327. By quantitatively comparing Balmer and oxygen line ratios of these galaxies with various low-redshift ‘analogue’ populations (e.g. Green Peas, Blueberries, etc.), we show that no single analogue population captures the diversity of line ratios of all three galaxies observed at z > 7.5. We find that S06355 at z = 7.67 and S10612 at z = 7.66 are similar to local Green Peas and Blueberries. In contrast, S04590 at z = 8.50 appears to be significantly different from the other two galaxies, most resembling extremely low-metallicity systems in the local Universe. Perhaps the most striking spectral feature in S04590 is the curiously high [O III] λ4363/[O III] λ5007 ratio (RO3) of 0.048 (or 0.055 when dust-corrected), implying either extremely high electron temperatures, >3 × 104 K, or gas densities >104 cm−3. Observed line ratios indicate that this galaxy is unlikely to host an AGN. Using photoionization modelling, we show that the inclusion of high-mass X-ray binaries or a high cosmic ray background in addition to a young, low-metallicity stellar population can provide the additional heating necessary to explain the observed high RO3 while remaining consistent with other observed line ratios. Our models represent a first step at accurately characterizing the dominant sources of photoionization and heating at very high redshifts, demonstrating that non-thermal processes may become important as we probe deeper into the Epoch of Reionization.Peer reviewe
JADES. The diverse population of infant Black Holes at 4<z<11: merging, tiny, poor, but mighty
We present 12 new AGN at 4<z<7 in the JADES survey (in addition to the
previously identified AGN in GN-z11 at z=10.6) revealed through the detection
of a Broad Line Region as seen in the Balmer emission lines. The depth of
JADES, together with the use of three different spectral resolutions, enables
us to probe a lower mass regime relative to previous studies. In a few cases we
find evidence for two broad components of Halpha which suggests that these
could be candidate merging black holes (BHs). The inferred BH masses range
between 8 x 10^7 Msun down to 4 x 10^5 Msun, interestingly probing the regime
expected for Direct Collapse Black Holes. The inferred AGN bolometric
luminosities (~10^44-10^45 erg/s) imply accretion rates that are < 0.5 times
the Eddington rate in most cases. However, small BH, with M_BH ~ 10^6 Msun,
tend to accrete at Eddington or super-Eddington rates. These BH at z~4-11 are
over-massive relative to their host galaxies stellar masses when compared to
the local M_BH-Mstar relation. However, we find that these early BH tend to be
more consistent with the local relation between M_BH and velocity dispersion,
as well as between M_BH and dynamical mass, suggesting that these are more
fundamental and universal relations. On the BPT excitation-diagnostic diagram
these AGN are located in the region that is that is locally occupied by
star-forming galaxies, implying that they would be missed by the standard
classification techniques if they did not display broad lines. Their location
on the diagram is consistent with what expected for AGN hosted in metal poor
galaxies (Z ~ 0.1-0.2 Zsun). The fraction of broad line AGN with L_AGN > 10^44
erg/s, among galaxies in the redshift range 4<z<6, is about 10%, suggesting
that the contribution of AGN and their hosts to the reionization of the
Universe is > 10%.Comment: Submitted to A&A, 25 pages, 13 figures, 4 table
The ionising photon production efficiency at z~6 for a sample of bright Lyman-alpha emitters using JEMS and MUSE
We study the ionising photon production efficiency at the end of the Epoch of
Reionisation () for a sample of 35 bright Lyman-
emitters, this quantity is crucial to infer the ionising photon budget of the
Universe. These objects were selected to have reliable spectroscopic redshifts,
assigned based on the profile of their Lyman- emission line, detected
in the MUSE deep fields. We exploit medium-band observations from the JWST
extragalactic medium band survey (JEMS) to find the flux excess corresponding
to the redshifted \ha\ emission line. We estimate the UV luminosity by fitting
the full JEMS photometry, along with several HST photometric points, with
\texttt{Prospector}. We find a median ultra-violet continuum slope of for the sample, indicating young stellar populations
with little-to-no dust attenuation. Supported by this, we derive
with no dust attenuation and find a median value of
log. If we
perform dust attenuation corrections and assume a Calzetti attenuation law, our
values are lowered by dex. Our results suggest Lyman-
emitters at the Epoch of Reionisation have enhanced compared to
previous estimations from literature, in particular, when compared to the
non-Lyman- emitting population. This initial study provides a promising
outlook on the characterisation of ionising photon production in the early
Universe. In the future, a more extensive study will be performed on the entire
dataset provided by the JWST Advanced Deep Extragalactic Survey (JADES). Thus,
for the first time, allowing us toComment: 11 pages, 5 figures in main paper. 10 pages, 30 figures in appendix.
Submitted to MNRA
The UV Continuum Slopes of Early Star-Forming Galaxies in JADES
The power-law slope of the rest-UV continuum
() is a key metric of early star forming
galaxies, providing one of our only windows into the stellar populations and
physical conditions of galaxies. Expanding upon previous studies with
limited sample sizes, we leverage deep imaging from JADES to investigate the UV
slopes of 179 galaxies with apparent magnitudes of ,
which display a median UV slope of . We compare to a statistical
sample of galaxies, finding a shift toward bluer rest-UV colors at all
. The most UV-luminous galaxies are significantly bluer than
their lower-redshift counterparts, representing a dearth of moderately-red
galaxies in the first Myr. At yet earlier times, the galaxy
population exhibits very blue UV slopes, implying very low attenuation from
dust. We identify a robust sample of 44 galaxies with , which have
SEDs requiring models of density-bounded HII regions and median ionizing photon
escape fractions of to reproduce. Their rest-optical colors imply that
this sample has weaker emission lines (median mag) than typical galaxies (median mag), consistent with the inferred escape fractions. This sample
has relatively low stellar masses (median ), and
specific star-formation rates (median) nearly twice that of our
full sample (median), suggesting they are more common among systems
experiencing a recent upturn in star formation. We demonstrate that the shutoff
of star formation provides an alternative solution for modelling of extremely
blue UV colors, making distinct predictions for the rest-optical emission of
these galaxies. Future spectroscopy will be required to distinguish between
these physical pictures.Comment: 17 pages, 13 figures; submitted to MNRA
The UV continuum slopes of early star-forming galaxies in JADES
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/The power-law slope of the rest-ultraviolet (UV) continuum (fλ ∝ λβ) is a key metric of early star-forming galaxies, providing one of our only windows into the stellar populations and physical conditions of z ≳ 10 galaxies. Expanding upon previous studies with limited sample sizes, we leverage deep imaging from the JWST Advanced Deep Extragalactic Survey (JADES) to investigate the UV slopes of 179 z ≳ 9 galaxies with apparent magnitudes of mF200W ≃ 26–31, which display a median UV slope of β = −2.4. We compare to a statistical sample of z ≃ 5–9 galaxies, finding a shift towards bluer rest-UV colours at all . The most UV-luminous z ≳ 9 galaxies are significantly bluer than their lower redshift counterparts, representing a dearth of moderately red galaxies within the first 500 Myr. At yet earlier times, the z ≳ 11 galaxy population exhibits very blue UV slopes, implying very low impact from dust attenuation. We identify a robust sample of 44 galaxies with β ≲ −2.8, which have spectral energy distributions requiring models of density-bounded H ii regions and median ionizing photon escape fractions of 0.51 to reproduce. Their rest-optical colours imply that this sample has weaker emission lines (median mF356W − mF444W = 0.19 mag) than typical galaxies (median mF356W − mF444W = 0.39 mag), consistent with the inferred escape fractions. This sample consists of relatively low stellar masses (median ), and specific star formation rates (sSFRs; median ) nearly twice that of our full galaxy sample (median sSFRs ), suggesting these objects are more common among systems experiencing a recent upturn in star formation. We demonstrate that the shutoff of star formation provides an alternative solution for modelling of extremely blue UV colours, making distinct predictions for the rest-optical emission of these galaxies. Future spectroscopy will be required to distinguish between these physical pictures.Peer reviewe
JADES: Resolving the Stellar Component and Filamentary Overdense Environment of HST-Dark Submillimeter Galaxy HDF850.1 at
HDF850.1 is the brightest submillimeter galaxy (SMG) in the Hubble Deep
Field. It is known as a heavily dust-obscured star-forming galaxy embedded in
an overdense environment at . With nine-band NIRCam images at 0.8-5.0
m obtained through the JWST Advanced Deep Extragalactic Survey (JADES), we
detect and resolve the rest-frame UV-optical counterpart of HDF850.1, which
splits into two components because of heavy dust obscuration in the center. The
southern component leaks UV and H photons, bringing the galaxy
100 times above the empirical relation between infrared excess and UV
continuum slope (IRX-). The northern component is higher in
dust attenuation and thus fainter in UV and H surface brightness. We
construct a spatially resolved dust attenuation map from the NIRCam images,
well matched with the dust continuum emission obtained through millimeter
interferometry. The whole system hosts a stellar mass of
and star-formation rate of
, placing the galaxy at the
massive end of the star-forming main sequence at this epoch. We further confirm
that HDF850.1 resides in a complex overdense environment at ,
which hosts another luminous SMG at (GN10). The filamentary structures
of the overdensity are characterized by 109 H-emitting galaxies
confirmed through NIRCam slitless spectroscopy at 3.9-5 m, of which only
eight were known before the JWST observations. Given the existence of a similar
galaxy overdensity in the GOODS-S field, our results suggest that % of
the cosmic star formation at occur in protocluster environments.Comment: 44 pages, 16 figures, 2 tables. Resubmitted to ApJ after including
the first-round referee's comment
JADES: Resolving the Stellar Component and Filamentary Overdense Environment of Hubble Space Telescope (HST)-dark Submillimeter Galaxy HDF850.1 at z = 5.18
© 2024 The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/HDF850.1 is the brightest submillimeter galaxy (SMG) in the Hubble Deep Field. It is known as a heavily dust-obscured star-forming galaxy embedded in an overdense environment at z = 5.18. With nine-band NIRCam images at 0.8–5.0 μm obtained through the JWST Advanced Deep Extragalactic Survey, we detect and resolve the rest-frame UV–optical counterpart of HDF850.1, which splits into two components because of heavy dust obscuration in the center. The southern component leaks UV and Hα photons, bringing the galaxy ∼100 times above the empirical relation between infrared excess and UV continuum slope (IRX–β UV). The northern component is higher in dust attenuation and thus fainter in UV and Hα surface brightness. We construct a spatially resolved dust-attenuation map from the NIRCam images, well matched with the dust continuum emission obtained through millimeter interferometry. The whole system hosts a stellar mass of 1010.8±0.1 M ⊙ and star formation rate (SFR) of 102.8±0.2 M ⊙ yr−1, placing the galaxy at the massive end of the star-forming main sequence at this epoch. We further confirm that HDF850.1 resides in a complex overdense environment at z = 5.17–5.30, which hosts another luminous SMG at z = 5.30 (GN10). The filamentary structures of the overdensity are characterized by 109 Hα-emitting galaxies confirmed through NIRCam slitless spectroscopy at 3.9–5 μm, of which only eight were known before the JWST observations. Given the existence of a similar galaxy overdensity in the GOODS-S field, our results suggest that 50% ± 20% of the cosmic star formation at z = 5.1–5.5 occur in protocluster environments.Peer reviewe
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