21 research outputs found
The Galaxy Starburst/Main-sequence Bimodality over Five Decades in Stellar Mass at z â 3â6.5
We study the relation between stellar mass (M*) and star formation rate (SFR)
for star-forming galaxies over approximately five decades in stellar mass (5.5
<~ log10(M*/Msun) <~ 10.5) at z ~ 3-6.5. This unprecedented coverage has been
possible thanks to the joint analysis of blank non-lensed fields (COSMOS/SMUVS)
and cluster lensing fields (Hubble Frontier Fields) which allow us to reach
very low stellar masses. Previous works have revealed the existence of a clear
bimodality in the SFR-M* plane with a star-formation Main Sequence and a
starburst cloud at z ~ 4-5. Here we show that this bimodality extends to all
star-forming galaxies and is valid in the whole redshift range z ~ 3-6.5. We
find that starbursts constitute at least 20% of all star-forming galaxies with
M* >~ 10^9 Msun at these redshifts and reach a peak of 40% at z=4-5. More
importantly, 60% to 90% of the total SFR budget at these redshifts is contained
in starburst galaxies, indicating that the starburst mode of star-formation is
dominant at high redshifts. Almost all the low stellar-mass starbursts with
log10(M*/Msun) <~ 8.5 have ages comparable to the typical timescales of a
starburst event, suggesting that these galaxies are being caught in the process
of formation. Interestingly, galaxy formation models fail to predict the
starburst/main-sequence bimodality and starbursts overall, suggesting that the
starburst phenomenon may be driven by physical processes occurring at smaller
scales than those probed by these models.Comment: 24 pages, including 15 figures (17 files in total) and 4 tables. The
manuscript has been accepted for publication in the Ap
Insight Into a Lensed -dark Galaxy and its Quiescent Companion at
Using the novel /NIRCam observations in the Abell 2744 field, we
present a first spatially resolved overview of an -dark galaxy,
spectroscopically confirmed at with magnification .
While being largely invisible at 1 m with NIRCam, except for sparse
clumpy sub-structures, the object is well-detected and resolved in the
long-wavelength bands with a spiral shape clearly visible in F277W. By
combining ancillary ALMA and data, we infer that this object is an
edge-on dusty spiral with an intrinsic stellar mass log
and a dust-obscured SFR~yr. A massive quiescent galaxy
(log) with tidal features lies 2\farcs{0} away
(9 kpc), at a consistent redshift as inferred by photometry,
indicating a potential major merger. The dusty spiral lies on the main-sequence
of star formation, and shows high dust attenuation in the optical (). In the far-infrared, its integrated dust SED is optically thick up to
m, further supporting the extremely dusty nature.
Spatially resolved analysis of the -dark galaxy reveals a largely uniform
area spanning 57 kpc, which spatially matches to
the ALMA 1 mm continuum emission. Accounting for the surface brightness dimming
and the depths of current surveys, unlensed analogs of the -dark
galaxy at would be only detectable in F356W and F444W in UNCOVER-like
survey, and become totally -dark at . This suggests that
detecting highly attenuated galaxies in the Epoch of Reionization might be a
challenging task for .Comment: 15 pages, 5 figures, 1 table. Accepted to ApJ
MIDIS: JWST/MIRI reveals the Stellar Structure of ALMA-selected Galaxies in the Hubble-UDF at Cosmic Noon
We present deep James Webb Space Telescope (JWST)/MIRI F560W observations of
a flux-limited, ALMA-selected sample of 28 galaxies at z=0.5-3.6 in the Hubble
Ultra Deep Field (HUDF). The data from the MIRI Deep Imaging Survey (MIDIS)
reveal the stellar structure of the HUDF galaxies at rest-wavelengths of >1
micron for the first time. We revise the stellar mass estimates using new JWST
photometry and find good agreement with pre-JWST analysis; the few
discrepancies can be explained by blending issues in the earlier
lower-resolution Spitzer data. At z~2.5, the resolved rest-frame near-infrared
(1.6 micron) structure of the galaxies is significantly more smooth and
centrally concentrated than seen by HST at rest-frame 450 nm (F160W), with
effective radii of Re(F560W)=1-5 kpc and S\'ersic indices mostly close to an
exponential (disk-like) profile (n~1), up to n~5 (excluding AGN). We find an
average size ratio of Re(F560W)/Re(F160W)~0.7 that decreases with stellar mass.
The stellar structure of the ALMA-selected galaxies is indistinguishable from a
HUDF reference sample of galaxies with comparable MIRI flux density. We
supplement our analysis with custom-made, position-dependent, empirical PSF
models for the F560W observations. The results imply that an older and smoother
stellar structure is in place in massive gas-rich, star-forming galaxies at
Cosmic Noon, despite a more clumpy rest-frame optical appearance, placing
additional constraints on galaxy formation simulations. As a next step,
matched-resolution, resolved ALMA observations will be crucial to further link
the mass- and light-weighted galaxy structures to the dusty interstellar
medium.Comment: 19 pages, 10 figures, 1 table, submitted to Ap
MIDIS. JWST NIRCam and MIRI unveil the stellar population properties of Ly-emitters and Lyman-Break galaxies at z ~ 3-7
We study the stellar population properties of 182 spectroscopically-confirmed
(MUSE/VLT) Lyman- emitters (LAEs) and 450 photometrically-selected
Lyman-Break galaxies (LBGs) at z = 2.8 - 6.7 in the Hubble eXtreme Deep Field
(XDF). Leveraging the combined power of HST and JWST NIRCam and MIRI
observations, we analyse their rest-frame UV-through-near-IR spectral energy
distributions (SEDs) with MIRI playing a crucial role in robustly assessing the
LAE's stellar mass and ages. Our LAEs are low-mass objects
(log(M[M]) ~ 7.5), with little or no dust extinction
(E(B - V) ~ 0.1) and a blue UV continuum slope ( ~ -2.2). While 75% of
our LAEs are young (< 100 Myr), the remaining 25% have significantly older
stellar populations (> 100 Myr). These old LAEs are statistically more massive,
less extinct and have lower specific star formation rate (sSFR) compared to
young LAEs. Besides, they populate the M - SFR plane along the
main-sequence (MS) of star-forming galaxies, while young LAEs populate the
starburst region. The comparison between the LAEs properties to those of a
stellar-mass matched sample of LBGs shows no statistical difference between
these objects, except for the LBGs redder UV continuum slope and marginally
larger E(B - V) values. Interestingly, 48% of the LBGs have ages < 10 Myr and
are classified as starbursts, but lack detectable Ly emission. This is
likely due to HI resonant scattering and/or selective dust extinction. Overall,
we find that JWST observations are crucial in determining the properties of
LAEs and shedding light on the properties and similarities between LAEs and
LBGs.Comment: 19 pages, 15 figures, 5 tables. Submitted to AP
Life beyond 30: Probing the-20 < M (UV) <-17 Luminosity Function at 8 < z < 13 with the NIRCam Parallel Field of the MIRI Deep Survey
We present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 8 galaxy candidates based on their dropout nature in the F115W and/or F150W filters, a high probability for their photometric redshifts, estimated with three different codes, being at z > 8, good fits based on Ï 2 calculations, and predominant solutions compared to z < 8 alternatives. We find mild evolution in the luminosity function from z ⌠13 to z ⌠8, i.e., only a small increase in the average number density of âŒ0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values α = â 2.2 ± 0.1, and M * = â 20.8 ± 0.2 mag. Comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses âŒ108 M â during the first 350 Myr of the universe, z ⌠12, with models matching better the luminosity density observational estimations âŒ150 Myr later, by z ⌠9
Life beyond 30: Probing the â20 < M UV < â17 Luminosity Function at 8 < z < 13 with the NIRCam Parallel Field of the MIRI Deep Survey
We present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 8 galaxy candidates based on their dropout nature in the F115W and/or F150W filters, a high probability for their photometric redshifts, estimated with three different codes, being at z > 8, good fits based on Ï2 calculations, and predominant solutions compared to z < 8 alternatives. We find mild evolution in the luminosity function from z ⌠13 to z ⌠8, i.e., only a small increase in the average number density of âŒ0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values α = â 2.2 ± 0.1, and M* = â 20.8 ± 0.2 mag. Comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses âŒ108Mâ during the first 350 Myr of the universe, z ⌠12, with models matching better the luminosity density observational estimations âŒ150 Myr later, by z ⌠9
Caratterizzazione delle Sorgenti Gamma dell'Osservatorio Fermi
Questa tesi tratta di sorgenti gamma extragalattiche scoperte con l'osservatorio Fermi. Tra l'altro, tramite un diagramma basato sul rapporto tra le densitĂ di flusso di energia nelle bande dello spettro elettromagnetico
X, radio e gamma ed Ăš a partire dai dati del catalogo 2FGL, si Ăš potuto ricavare un efficace metodo per l'associazione di sorgenti Gamma con le rispettive contropart
Constraints on the Faint End of the Galaxy Stellar Mass Function at z â 4-8 from Deep JWST Data
We analyze a sample of 3300 galaxies between redshifts z â 3.5 and z â 8.5 selected from James Webb Space Telescope (JWST) images in the Hubble Ultra Deep Field and UKIDSS Ultra Deep Survey field, including objects with stellar masses as low as â108 M â up to z â 8. The depth and wavelength coverage of the JWST data allows us, for the first time, to derive robust stellar masses for such high-z, low stellar mass galaxies on an individual basis. We compute the galaxy stellar mass function, after complementing our sample with ancillary data from CANDELS to constrain the GMSF at high stellar masses ( M > M * ). Our results show a steepening of the low stellar mass end slope (α) with redshift, with α = â1.61 ± 0.05 at z â 4 and α = â1.98 ± 0.14 at z â 7. We also observe an evolution of the normalization Ï * from z â 7 to z â 4, with Ï z â 4 * / Ï z â 7 * = 130 â 50 + 210 . Our study incorporates a novel method for the estimation of the Eddington bias, which takes into account its possible dependence both on stellar mass and redshift, while allowing for skewness in the error distribution. We finally compute the resulting cosmic stellar mass density and find a flatter evolution with redshift than previous studies.</p
Constraints on the Faint End of the Galaxy Stellar Mass Function at z â 4-8 from Deep JWST Data
We analyze a sample of 3300 galaxies between redshifts z â 3.5 and z â 8.5 selected from James Webb Space Telescope (JWST) images in the Hubble Ultra Deep Field and UKIDSS Ultra Deep Survey field, including objects with stellar masses as low as â108 M â up to z â 8. The depth and wavelength coverage of the JWST data allows us, for the first time, to derive robust stellar masses for such high-z, low stellar mass galaxies on an individual basis. We compute the galaxy stellar mass function, after complementing our sample with ancillary data from CANDELS to constrain the GMSF at high stellar masses ( M > M * ). Our results show a steepening of the low stellar mass end slope (α) with redshift, with α = â1.61 ± 0.05 at z â 4 and α = â1.98 ± 0.14 at z â 7. We also observe an evolution of the normalization Ï * from z â 7 to z â 4, with Ï z â 4 * / Ï z â 7 * = 130 â 50 + 210 . Our study incorporates a novel method for the estimation of the Eddington bias, which takes into account its possible dependence both on stellar mass and redshift, while allowing for skewness in the error distribution. We finally compute the resulting cosmic stellar mass density and find a flatter evolution with redshift than previous studies.</p
JWST unveils heavily obscured (active and passive) sources up to z âŒ13
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 Mâ âŒ109-11 M· at 8 < z < 13 characterized by unexpectedly important dust content at those epochs (AV up to âŒ5.8 mag), challenging current model predictions. We further identify an extremely red source (F200W-F440W âŒ7 mag) that can be reproduced only by the spectrum of a passive, quenched galaxy of Mâ âŒ1011.56 M· at z âŒ5, filled of dust (AV âŒ5 mag).</p