20 research outputs found
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
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
The probability of galaxy-galaxy strong lensing events in hydrodynamical simulations of galaxy clusters
Meneghetti et al. (2020) recently reported an excess of galaxy-galaxy strong
lensing (GGSL) in galaxy clusters compared to expectations from the LCDM
cosmological model. Theoretical estimates of the GGSL probability are based on
the analysis of numerical hydrodynamical simulations in the LCDM cosmology. We
quantify the impact of the numerical resolution and AGN feedback scheme adopted
in cosmological simulations on the predicted GGSL probability and determine if
varying these simulation properties can alleviate the gap with observations. We
repeat the analysis of Meneghetti et al. (2020) on cluster-size halos simulated
with different mass and force resolutions and implementing several independent
AGN feedback schemes. We find that improving the mass resolution by a factor of
ten and twenty-five, while using the same galaxy formation model that includes
AGN feedback, does not affect the GGSL probability. We find similar results
regarding the choice of gravitational softening. On the contrary, adopting an
AGN feedback scheme that is less efficient at suppressing gas cooling and star
formation leads to an increase in the GGSL probability by a factor between
three and six. However, we notice that such simulations form overly massive
subhalos whose contribution to the lensing cross-section would be significant
while their Einstein radii are too large to be consistent with the
observations. The primary contributors to the observed GGSL cross-sections are
subhalos with smaller masses, that are compact enough to become critical for
lensing. The population with these required characteristics appears to be
absent in simulations.Comment: 13 pages, 11 figures. Submitted for publication on Astronomy and
Astrophysic
Early Results from GLASS-JWST. XIX: A High Density of Bright Galaxies at in the Abell 2744 Region
We report the detection of a high density of redshift galaxies
behind the foreground cluster Abell 2744, selected from imaging data obtained
recently with NIRCam onboard {\it JWST} by three programs -- GLASS-JWST,
UNCOVER, and DDT\#2756. To ensure robust estimates of the lensing magnification
, we use an improved version of our model that exploits the first epoch of
NIRCam images and newly obtained MUSE spectra, and avoids regions with
where the uncertainty may be higher. We detect seven bright
galaxies with demagnified rest-frame mag,
over an area of sq. arcmin. Taking into account photometric
incompleteness and the effects of lensing on luminosity and cosmological
volume, we find that the density of galaxies in the field is
about () larger than the average at mag reported so far. The density is even higher when considering only
the GLASS-JWST data, which are the deepest and the least affected by
magnification and incompleteness. The GLASS-JWST field contains 5 out of 7
galaxies, distributed along an apparent filamentary structure of 2 Mpc in
projected length, and includes a close pair of candidates with mag having a projected separation of only 16 kpc. These findings suggest
the presence of a overdensity in the field. In addition to
providing excellent targets for efficient spectroscopic follow-up observations,
our study confirms the high density of bright galaxies observed in early {\it
JWST} observations, but calls for multiple surveys along independent lines of
sight to achieve an unbiased estimate of their average density and a first
estimate of their clustering.Comment: Accepted for publication in ApJL, 13 pages, 4 figure
The Dark Energy Survey : more than dark energy â an overview
This overview paper describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is using a wide-field camera (DECam) on the 4 m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion, the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. In addition, a time-domain survey search over 27 sq deg is expected to yield a sample of thousands of Type Ia supernovae and other transients. The main goals of DES are to characterize dark energy and dark matter, and to test alternative models of gravity; these goals will be pursued by studying large-scale structure, cluster counts, weak gravitational lensing and Type Ia supernovae. However, DES also provides a rich data set which allows us to study many other aspects of astrophysics. In this paper, we focus on additional science with DES, emphasizing areas where the survey makes a difference with respect to other current surveys. The paper illustrates, using early data (from âScience Verificationâ, and from the first, second and third seasons of observations), what DES can tell us about the Solar system, the Milky Way, galaxy evolution, quasars and other topics. In addition, we show that if the cosmological model is assumed to be +cold dark matter, then important astrophysics can be deduced from the primary DES probes. Highlights from DES early data include the discovery of 34 trans-Neptunian objects, 17 dwarf satellites of the Milky Way, one published z > 6 quasar (and more confirmed) and two published superluminous supernovae (and more confirmed)
VLT/MUSE Observations of SDSS J1029+2623:Toward a High-precision Strong Lensing Model
We present a strong lensing analysis of the galaxy cluster SDSS J1029+2623 at
, one of the few currently known lens clusters with multiple images of
a background () quasar with a measured time delay. We use archival
Hubble Space Telescope multi-band imaging and new Multi Unit Spectroscopic
Explorer follow-up spectroscopy to build an accurate lens mass model, a crucial
step towards future cosmological applications. The spectroscopic data enable
the secure identification of 57 cluster members and of two nearby perturbers
along the line-of-sight. We estimate the inner kinematics of a sub-set of 20
cluster galaxies to calibrate the scaling relations parametrizing the sub-halo
mass component. We also reliably determine the redshift of 4 multiply imaged
sources, provide a tentative measurement for one system, and report the
discovery of a new four-image system. The final catalog comprises 26 multiple
images from 7 background sources, spanning a wide redshift range, from 1.02 to
5.06. We present two parametric lens models, with slightly different cluster
mass parametrizations. The observed positions of the multiple images are
accurately reproduced within approximately , the three image positions
of the quasar within only . We estimate a cluster projected total
mass of , with a
statistical uncertainty of a few percent. Both models, that include a small
galaxy close to one of the quasar images, predict magnitude differences and
time delays between the quasar images that are consistent with the
observations.Comment: 24 pages, 10 figures, 6 Tables. Submitted to ApJ. The full MUSE
spectroscopic catalog of SDSS J1029+2623 presented here is made publicly
available at https://www.fe.infn.it/astro/lensin
The abundance of compact quiescent galaxies since
International audienceWe set out to quantify the number density of quiescent massive compact galaxies at intermediate redshifts. We determine structural parameters based on i-band imaging using the CanadaâFranceâHawaii Telescope (CFHT) equatorial Sloan Digital Sky Survey (SDSS) Stripe 82 (CS82) survey (âŒ170 deg^2) taking advantage of an exquisite median seeing of âŒ0.6 arcsec. We select compact massive (M_â > 5 Ă 10^10âM_â) galaxies within the redshift range of 0.2 10. We systematically measure a factor of âŒ5 more compacts at the same redshift than what was previously reported on smaller fields with Hubble Space Telescope (HST) imaging, which are more affected by cosmic variance. This means that the decrease in number density from z âŒÂ 1.5 to z âŒÂ 0.2 might be only of a factor of âŒ2â5, significantly smaller than what was previously reported. This supports progenitor bias as the main contributor to the size evolution. This milder decrease is roughly compatible with the predictions from recent numerical simulations. Only the most extreme compact galaxies, with R_eff  10^10.7âM_â, appear to drop in number by a factor of âŒ20 and hence likely experience a noticeable size evolution