108 research outputs found
The cosmic assembly of stellar haloes in massive Early-Type Galaxies
Using the exquisite depth of the Hubble Ultra Deep Field (HUDF12 programme) data set, we explore the ongoing assembly of the outermost regions of the most massive galaxies (Mstellar ≥ 5× 1010 M⊙) at z ≤ 1. The outskirts of massive objects, particularly early-type Galaxies (ETGs), are expected to suffer a dramatic transformation across cosmic time due to continuous accretion of small galaxies. HUDF imaging allows us to study this process at intermediate redshifts in six massive galaxies, exploring the individual surface brightness profiles out to ∼25 effective radii. We find that 5–20 per cent of the total stellar mass for the galaxies in our sample is contained within 10 1–2 per cent, very similar to predictions based on observed close pair counts. Therefore, the results for our small albeit meaningful sample suggest that the size and mass growth of the most massive galaxies have been solely driven by minor and major merging from z = 1 to today
NIR Spectroscopy of Star-Forming Galaxies at z~1.4 with Subaru/FMOS: The Mass-Metallicity Relation
We present near-infrared spectroscopic observations of star-forming galaxies
at z~1.4 with FMOS on the Subaru Telescope. We observed K-band selected
galaxies in the SXDS/UDS fields with K10^{9.5}
Msun, and expected F(Halpha)>10^{-16} erg s^{-1} cm^{-2}. 71 objects in the
sample have significant detections of Halpha. For these objects, excluding
possible AGNs identified from the BPT diagram, gas-phase metallicities are
obtained from [NII]/Halpha line ratio. The sample is split into three stellar
mass bins, and the spectra are stacked in each stellar mass bin. The
mass-metallicity relation obtained at z~1.4 is located between those at z~0.8
and z~2.2. We constrain an intrinsic scatter to be ~0.1 dex or larger in the
mass-metallicity relation at z~1.4; the scatter may be larger at higher
redshifts. We found trends that the deviation from the mass-metallicity
relation depends on the SFR and the half light radius: Galaxies with higher SFR
and larger half light radii show lower metallicities at a given stellar mass.
One possible scenario for the trends is the infall of pristine gas accreted
from IGM or through merger events. Our data points show larger scatter than the
fundamental metallicity relation (FMR) at z~0.1 and the average metallicities
slightly deviate from the FMR. The compilation of the mass-metallicity
relations at z~3 to z~0.1 shows that they evolve smoothly from z~3 to z~0
without changing the shape so much except for the massive part at z~0.Comment: 20 pages, 18 figures, accepted for publication in PAS
New Constraints on Cosmic Reionization from the 2012 Hubble Ultra Deep Field Campaign
Understanding cosmic reionization requires the identification and
characterization of early sources of hydrogen-ionizing photons. The 2012 Hubble
Ultra Deep Field (UDF12) campaign has acquired the deepest infrared images with
the Wide Field Camera 3 aboard Hubble Space Telescope and, for the first time,
systematically explored the galaxy population deep into the era when cosmic
microwave background (CMB) data indicates reionization was underway. The UDF12
campaign thus provides the best constraints to date on the abundance,
luminosity distribution, and spectral properties of early star-forming
galaxies. We synthesize the new UDF12 results with the most recent constraints
from CMB observations to infer redshift-dependent ultraviolet (UV) luminosity
densities, reionization histories, and electron scattering optical depth
evolution consistent with the available data. Under reasonable assumptions
about the escape fraction of hydrogen ionizing photons and the intergalactic
medium clumping factor, we find that to fully reionize the universe by redshift
z~6 the population of star-forming galaxies at redshifts z~7-9 likely must
extend in luminosity below the UDF12 limits to absolute UV magnitudes of
M_UV\sim -13 or fainter. Moreover, low levels of star formation extending to
redshifts z~15-25, as suggested by the normal UV colors of z\simeq7-8 galaxies
and the smooth decline in abundance with redshift observed by UDF12 to
z\simeq10, are additionally likely required to reproduce the optical depth to
electron scattering inferred from CMB observations.Comment: Version accepted by ApJ (originally submitted Jan 5, 2013). The UDF12
website can be found at http://udf12.arizona.ed
Ultraviolet/Optical Emission Of The Ionised Gas In Agn: Diagnostics Of The Ionizing Source And Gas Properties
Spectroscopic studies of active galactic nuclei (AGN) are powerful means of probing the physical properties of the ionized gas within them. In particular, near future observational facilities, such as the James Webb Space Telescope (JWST), will allow detailed statistical studies of rest-frame ultraviolet and optical spectral features of the very distant AGN with unprecedented accuracy. In this proceedings, we discuss the various ways of exploiting new dedicated photoionization models of the narrow-line emitting regions (NLR) of AGN for the interpretation of forthcoming revolutionary datasets
The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources
We report the multi-wavelength identification of the X-ray sources found in
the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the
wavelength range between the far-UV to the mid-IR. We select a primary
counterpart of each X-ray source by applying the likelihood ratio method to
R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching
catalogs of AGN candidates selected in 1.4GHz radio and i'-band variability
surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a
nearby galaxy, and clusters of galaxies are removed there are 896 AGN
candidates in the sample. We conduct spectroscopic observations of the primary
counterparts with multi-object spectrographs in the optical and NIR; 65\% of
the X-ray AGN candidates are spectroscopically-identified. For the remaining
X-ray AGN candidates, we evaluate their photometric redshift with photometric
data in 15 bands. Utilising the multi-wavelength photometric data of the large
sample of X-ray selected AGNs, we evaluate the stellar masses, M*, of the host
galaxies of the narrow-line AGNs. The distribution of the stellar mass is
remarkably constant from z=0.1 to 4.0. The relation between M* and 2--10 keV
luminosity can be explained with strong cosmological evolution of the
relationship between the black hole mass and M*. We also evaluate the scatter
of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a
function of X-ray luminosity and absorption to the nucleus. The scatter is
compared with galaxies which have redshift and stellar mass distribution
matched with the X-ray AGN. The UV-NIR SEDs of obscured X-ray AGNs are similar
to those of the galaxies in the matched sample. In the NIR-MIR range, the
median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray
AGN broadly overlaps that of the galaxies in the matched sample.Comment: Accepted for publication in PASJ Subaru special issue. 42 pages, 22
figures. Entire contents of Tables 3, 8, 9, 10, and 11, and ASCII format
tables are available from
http://www.astr.tohoku.ac.jp/~akiyama/SXDS/index.htm
The UV Luminosity Function of Star-forming Galaxies via Dropout Selection at Redshifts z ~ 7 and 8 from the 2012 Ultra Deep Field Campaign
We present a catalog of high-redshift star-forming galaxies selected to lie within the redshift range z ≃ 7-8 using the Ultra Deep Field 2012 (UDF12), the deepest near-infrared (near-IR) exposures yet taken with the Hubble Space Telescope (HST). As a result of the increased near-IR exposure time compared to previous HST imaging in this field, we probe ~0.65 (0.25) mag fainter in absolute UV magnitude, at z ~ 7 (8), which increases confidence in a measurement of the faint end slope of the galaxy luminosity function. Through a 0.7 mag deeper limit in the key F105W filter that encompasses or lies just longward of the Lyman break, we also achieve a much-refined color-color selection that balances high redshift completeness and a low expected contamination fraction. We improve the number of dropout-selected UDF sources to 47 at z ~ 7 and 27 at z ~ 8. Incorporating brighter archival and ground-based samples, we measure the z ≃ 7 UV luminosity function to an absolute magnitude limit of M_(UV) = –17 and find a faint end Schechter slope of ɑ =-1.87^(+0.18)_(-0.17). Using a similar color-color selection at z ≃ 8 that takes our newly added imaging in the F140W filter into account, and incorporating archival data from the HIPPIES and BoRG campaigns, we provide a robust estimate of the faint end slope at z ≃ 8, ɑ =-1.94^(+0.21)_(-0.24). We briefly discuss our results in the context of earlier work and that derived using the same UDF12 data but with an independent photometric redshift technique
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: Using NIRCam Photometry to Investigate the Dependence of Stellar Mass Inferences on the IMF in the Early Universe
The detection of numerous and relatively bright galaxies at redshifts z > 9
has prompted new investigations into the star-forming properties of
high-redshift galaxies. Using local forms of the initial mass function (IMF) to
estimate stellar masses of these galaxies from their light output leads to
galaxy masses that are at the limit allowed for the state of the LambdaCDM
Universe at their redshift. We explore how varying the IMF assumed in studies
of galaxies in the early universe changes the inferred values for the stellar
masses of these galaxies. We infer galaxy properties with the SED fitting code
Prospector using varying IMF parameterizations for a sample of 102 galaxies
from the JWST Advanced Deep Extragalactic Survey (JADES) spectroscopically
confirmed to be at z > 6.7, with additional photometry from the JWST
Extragalactic Medium Band Survey (JEMS) for twenty-one galaxies. We demonstrate
that models with stellar masses reduced by a factor of three or more do not
affect the modeled spectral energy distribution (SED).Comment: The Significance statement is required for PNAS submissio
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
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