55 research outputs found
On the accuracy of the Perturbative Approach for Strong Lensing: Local Distortion for Pseudo-Elliptical Models
The Perturbative Approach (PA) introduced by \citet{alard07} provides
analytic solutions for gravitational arcs by solving the lens equation
linearized around the Einstein ring solution. This is a powerful method for
lens inversion and simulations in that it can be used, in principle, for
generic lens models. In this paper we aim to quantify the domain of validity of
this method for three quantities derived from the linearized mapping: caustics,
critical curves, and the deformation cross section (i.e. the arc cross section
in the infinitesimal circular source approximation). We consider lens models
with elliptical potentials, in particular the Singular Isothermal Elliptic
Potential and Pseudo-Elliptical Navarro--Frenk--White models. We show that the
PA is exact for this first model. For the second, we obtain constraints on the
model parameter space (given by the potential ellipticity parameter
and characteristic convergence ) such that the PA is
accurate for the aforementioned quantities. In this process we obtain analytic
expressions for several lensing functions, which are valid for the PA in
general. The determination of this domain of validity could have significant
implications for the use of the PA, but it still needs to be probed with
extended sources.Comment: Accepted for publication in MNRA
The Galaxy Starburst/Main-sequence Bimodality over Five Decades in Stellar Mass at z ≈ 3–6.5
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
Weak-lensing calibration of a stellar mass-based mass proxy for redMaPPer and Voronoi Tessellation clusters in SDSS Stripe 82
We present the first weak lensing calibration of , a new galaxy
cluster mass proxy corresponding to the total stellar mass of red and blue
members, in two cluster samples selected from the SDSS Stripe 82 data: 230
redMaPPer clusters at redshift and 136 Voronoi Tessellation
(VT) clusters at . We use the CS82 shear catalog and stack
the clusters in bins to measure a mass-observable power law
relation. For redMaPPer clusters we obtain , . For VT clusters, we find
, and , for a low and a high redshift bin, respectively. Our results are
consistent, internally and with the literature, indicating that our method can
be applied to any cluster finding algorithm. In particular, we recommend that
be used as the mass proxy for VT clusters. Catalogs including
measurements will enable its use in studies of galaxy evolution
in clusters and cluster cosmology.Comment: Updated to be consistent with the published versio
The SOAR Gravitational Arc Survey - I: Survey overview and photometric catalogs
We present the first results of the SOAR (Southern Astrophysical Research)
Gravitational Arc Survey (SOGRAS). The survey imaged 47 clusters in two
redshift intervals centered at and , targeting the richest
clusters in each interval. Images were obtained in the , and
bands using the SOAR Optical Imager (SOI), with a median seeing of 0.83, 0.76
and 0.71 arcsec, respectively, in these filters. Most of the survey clusters
are located within the Sloan Digital Sky Survey (SDSS) Stripe 82 region and all
of them are in the SDSS footprint. Photometric calibration was therefore
performed using SDSS stars located in our SOI fields. We reached for galaxies
in all fields the detection limits of , and for a signal-to-noise ratio (S/N) = 3. As a by-product of the image
processing, we generated a source catalogue with 19760 entries, the vast
majority of which are galaxies, where we list their positions, magnitudes and
shape parameters. We compared our galaxy shape measurements to those of local
galaxies and concluded that they were not strongly affected by seeing. From the
catalogue data, we are able to identify a red sequence of galaxies in most
clusters in the lower range. We found 16 gravitational arc candidates
around 8 clusters in our sample. They tend to be bluer than the central
galaxies in the lensing cluster. A preliminary analysis indicates that of the clusters have arcs around them, with a possible indication of a
larger efficiency associated to the high- systems when compared to the
low- ones. Deeper follow-up images with Gemini strengthen the case for the
strong lensing nature of the candidates found in this survey.Comment: 17 pages, 11 figures (most of them multi-panel) MNRAS (2013
Systematic search for lensed X-ray sources in the CLASH fields
We search for unresolved X-ray emission from lensed sources in the FOV of 11
CLASH clusters with Chandra data. We consider the solid angle in the lens plane
corresponding to a magnification , that amounts to a total of ~100
arcmin. Our main goal is to assess the efficiency of massive clusters as
cosmic telescopes to explore the faint end of X-ray extragalactic source
population. We search for X-ray emission from strongly lensed sources
identified in the optical, and perform an untargeted detection of lensed X-ray
sources. We detect X-ray emission only in 9 out of 849 lensed/background
optical sources. The stacked emission of the sources without detection does not
reveal any signal in any band. Based on the untargeted detection, we find 66
additional X-ray sources that are consistent with being lensed sources. After
accounting for completeness and sky coverage, we measure for the first time the
soft- and hard-band number counts of lensed X-ray sources. The results are
consistent with current modelization of the AGN population distribution. The
distribution of de-lensed fluxes of the sources identified in moderately deep
CLASH fields reaches a flux limit of ~ and ~ erg/s/cm
in the soft and hard bands, respectively. We conclude that, in order to match
the depth of the CDFS exploiting massive clusters as cosmic telescopes, the
required number of cluster fields is about two orders of magnitude larger than
that offered by the 20 years Chandra archive. A significant step forward will
be made when future X-ray facilities, with ~1' angular resolution and large
effective area, will allow the serendipitous discovery of rare, strongly lensed
high- X-ray sources, enabling the study of faint AGN activity in early
Universe and the measurement of gravitational time delays in the X-ray
variability of multiply imaged AGN.Comment: Accepted for publication in A&
Exploring the low-mass regime of galaxy-scale strong lensing: Insights into the mass structure of cluster galaxies
We aim at a direct measurement of the compactness of three galaxy-scale
lenses in massive clusters, testing the accuracy of the scaling laws that
describe the members in strong lensing (SL) models of galaxy clusters. We
selected the multiply imaged sources MACS J0416.12403 ID14 (), MACS
J0416.12403 ID16 (), and MACS J1206.20847 ID14 ().
Eight images were observed for the first SL system, and six for the latter two.
We focused on the main deflector of each galaxy-scale SL system (identified as
members 8971, 8785, and 3910, respectively), and modelled its total mass
distribution with a truncated isothermal sphere. We accounted for the lensing
effects of the remaining cluster components, and included the uncertainty on
the cluster-scale mass distribution through a bootstrapping procedure. We
measured a truncation radius value of ,
, and
for members 8971, 8785, and 3910, respectively. Alternative non-truncated
models with a higher number of free parameters do not lead to an improved
description of the SL system. We measured the stellar-to-total mass fraction
within the effective radius for the three members, finding ,
, and , respectively. We find that a parameterisation
of the properties of cluster galaxies in SL models based on power-law scaling
relations with respect to the total luminosity cannot accurately describe their
compactness over their full total mass range. Our results agree with modelling
of the cluster members based on the Fundamental Plane relation. Finally, we
report good agreement between our values of the stellar-to-total mass fraction
within and those of early-type galaxies from the SLACS Survey. Our work
significantly extends the regime of the current samples of lens galaxies.Comment: Astronomy & Astrophysics, 679, A124 (2023), 15 pages, 12 figures, 8
table
A multiwavelength study of a massive, active galaxy at z similar to 2:coupling the kinematics of the ionized and molecular gas
We report a multiwavelength study of the massive ( M-* greater than or similar to 10(11)M(circle dot)), z similar to 2 star-forming galaxy GMASS 0953, which hosts an obscured AGN. We combined near-infrared observations of the GNIRS, SINFONI and KMOS spectrographs to study the kinematics of the [O III] lambda 5007 and H alpha emission lines. Our analysis shows that GMASS 0953 may host an ionized disc extending up to 13 kpc, which rotates at a velocity of V-ion = 203(-20)(+17) km s(-1) at the outermost radius. Evidence of rotation on a smaller scale (R similar to 1 kpc) arises from the CO(J = 6-5) line. The central velocity V-CO = 320(-53)(+92) km s(-1) traced by the molecular gas is higher than V-ion, suggesting that the galaxy harbours a multiphase disc with a rotation curve that peaks in the very central regions. The galaxy appears well located on the z = 0 baryonic Tully-Fisher relation. We also discuss the possibility that the [O III] lambda 5007 and H alpha velocity gradients are due to a galactic-scale wind. Besides, we found evidence of an AGN-driven outflow traced by a broad blueshifted wing affecting the [O III] lambda 5007 line, which presents a velocity offset Delta v = -535 +/- 152 km s(-1) from the systemic velocity. Because of the short depletion time-scale (tau(dep) similar to 10(8) yr) due to gas ejection and gas consumption by star formation activity, GMASS 0953 may likely evolve into a passive galaxy. However, the role of the AGN in depleting the gas reservoir of the galaxy is quite unclear because of the uncertainties affecting the outflow rate
Constraints on the [C II] luminosity of a proto-globular cluster at z ∼ 6 obtained with ALMA
We report on ALMA observations of D1, a system at z 3c 6.15 with stellar mass M 17 3c 107M containing globular
cluster (GC) precursors, strongly magnified by the galaxy cluster MACS J0416.1-2403. Since the discovery of GC
progenitors at high redshift, ours is the first attempt to probe directly the physical properties of their neutral gas
through infrared observations. A careful analysis of our dataset, performed with a suitable procedure designed to
identify faint narrow lines and which can test various possible values for the unknown linewidth value, allowed us
to identify a 4\u3c3 tentative detection of [CII] emission with intrinsic luminosity L[CII] = (2.9 \ub1 1.4) 106L, one of the
lowest values ever detected at high redshift. This study offers a first insight on previously uncharted regions of the
L[CII] 12 SF R relation. Despite large uncertainties affecting our measure of the star formation rate, if taken at face
value our estimate lies more than 3c 1 dex below the values observed in local and high redshift systems. Our weak
detection indicates a deficiency of [CII] emission, possibly ascribed to various explanations, such as a low-density gas
and/or a strong radiation field caused by intense stellar feedback, and a low metal content. From the non-detection
in the continuum we derive constraints on the dust mass, with 3 12 \u3c3 upper limit values as low as 3c a few 104 M,
consistent with the values measured in local metal-poor galaxies
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