1,577 research outputs found
CLASH-VLT: Strangulation of cluster galaxies in MACSJ0416.1-2403 as seen from their chemical enrichment
(abridged) We explore the Frontier Fields cluster MACS J0416.1-2403 at
z=0.3972 with VIMOS/VLT spectroscopy from the CLASH-VLT survey covering a
region which corresponds to almost three virial radii. We measure fluxes of 5
emission lines of 76 cluster members enabling us to unambiguously derive O/H
gas metallicities, and also SFRs from Halpha. For intermediate massses we find
a similar distribution of cluster and field galaxies in the MZR and mass vs.
sSFR diagrams. Bulge-dominated cluster galaxies have on average lower sSFRs and
higher O/Hs compared to their disk-dominated counterparts. We use the location
of galaxies in the projected velocity vs. position phase-space to separate our
cluster sample into a region of objects accreted longer time ago and a region
of recently accreted and infalling galaxies. We find a higher fraction of
accreted metal-rich galaxies (63%) compared to the fraction of 28% of
metal-rich galaxies in the infalling regions. Intermediate mass galaxies
falling into the cluster for the first time are found to be in agreement with
predictions of the fundamental metallicity relation. In contrast, for already
accreted star-forming galaxies of similar masses, we find on average
metallicities higher than predicted by the models. This trend is intensified
for accreted cluster galaxies of the lowest mass bin, that display
metallicities 2-3 times higher than predicted by models with primordial gas
inflow. Environmental effects therefore strongly influence gas regulations and
control gas metallicities of log(M/Msun)<10.2 (Salpeter IMF) cluster galaxies.
We also investigate chemical evolutionary paths of model galaxies with and
without inflow of gas showing that strangulation is needed to explain the
higher metallicities of accreted cluster galaxies. Our results favor a
strangulation scenario in which gas inflow stops for log(M/Msun)<10.2 galaxies
when accreted by the cluster.Comment: Version better matched to the published version, including table with
observed and derived quantities for the 76 cluster galaxie
Discovery of a faint, star-forming, multiply lensed, Lyman-alpha blob
We report the discovery of a multiply lensed Lyman- blob (LAB) behind
the galaxy cluster AS1063 using the Multi Unit Spectroscopic Explorer (MUSE) on
the Very Large Telescope (VLT). The background source is at 3.117 and is
intrinsically faint compared to almost all previously reported LABs. We used
our highly precise strong lensing model to reconstruct the source properties,
and we find an intrinsic luminosity of =
erg s, extending to 33 kpc. We find that the LAB is associated with a
group of galaxies, and possibly a protocluster, in agreement with previous
studies that find LABs in overdensities. In addition to Lyman-
(Ly) emission, we find \ion{C}{IV}, \ion{He}{II}, and \ion{O}{III}]
ultraviolet (UV) emission lines arising from the centre of the nebula. We used
the compactness of these lines in combination with the line ratios to conclude
that the \Lya nebula is likely powered by embedded star formation. Resonant
scattering of the \Lya photons then produces the extended shape of the
emission. Thanks to the combined power of MUSE and strong gravitational
lensing, we are now able to probe the circumgalatic medium of sub-
galaxies at .Comment: 7 pages, 7 figures; moderate changes to match the accepted A&A
versoi
CLASH-VLT: Testing the Nature of Gravity with Galaxy Cluster Mass Profiles
We use high-precision kinematic and lensing measurements of the total mass
profile of the dynamically relaxed galaxy cluster MACS J1206.2-0847 at
to estimate the value of the ratio between the two scalar
potentials in the linear perturbed Friedmann-Lemaitre-Robertson-Walker
metric.[...] Complementary kinematic and lensing mass profiles were derived
from exhaustive analyses using the data from the Cluster Lensing And Supernova
survey with Hubble (CLASH) and the spectroscopic follow-up with the Very Large
Telescope (CLASH-VLT). Whereas the kinematic mass profile tracks only the
time-time part of the perturbed metric (i.e. only ), the lensing mass
profile reflects the contribution of both time-time and space-space components
(i.e. the sum ). We thus express as a function of the mass
profiles and perform our analysis over the radial range . Using a spherical Navarro-Frenk-White mass profile, which
well fits the data, we obtain \eta(r_{200})=1.01\,_{-0.28}^{+0.31} at the
68\% C.L. We discuss the effect of assuming different functional forms for mass
profiles and of the orbit anisotropy in the kinematic reconstruction.
Interpreting this result within the well-studied modified gravity model,
the constraint on translates into an upper bound to the interaction
length (inverse of the scalaron mass) smaller than 2 Mpc. This tight constraint
on the interaction range is however substantially relaxed when
systematic uncertainties in the analysis are considered. Our analysis
highlights the potential of this method to detect deviations from general
relativity, while calling for the need of further high-quality data on the
total mass distribution of clusters and improved control on systematic effects.Comment: 18 pages, 3 figures, submitted to JCA
Massive Star cluster formation under the microscope at z=6
We report on a superdense star-forming region with an effective radius (R_e)
smaller than 13 pc identified at z=6.143 and showing a star-formation rate
density \Sigma_SFR~1000 Msun/yr/kpc2 (or conservatively >300 Msun/yr/kpc2).
Such a dense region is detected with S/N>40 hosted by a dwarf extending over
440 pc, dubbed D1 (Vanzella et al. 2017b). D1 is magnified by a factor
17.4+/-5.0 behind the Hubble Frontier Field galaxy cluster MACS~J0416 and
elongated tangentially by a factor 13.2+/-4.0 (including the systematic
errors). The lens model accurately reproduces the positions of the confirmed
multiple images with a r.m.s. of 0.35", and the tangential stretch is well
depicted by a giant multiply-imaged Lya arc. D1 is part of an interacting
star-forming complex extending over 800 pc. The SED-fitting, the very blue
ultraviolet slope (\beta ~ -2.5, F(\lambda) ~ \lambda^\beta) and the prominent
Lya emission of the stellar complex imply that very young (< 10-100 Myr),
moderately dust-attenuated (E(B-V)<0.15) stellar populations are present and
organised in dense subcomponents. We argue that D1 (with a stellar mass of 2 x
10^7 Msun) might contain a young massive star cluster of M < 10^6 Msun and
Muv~-15.6 (or m_uv=31.1), confined within a region of 13 pc, and not dissimilar
from some local super star clusters (SSCs). The ultraviolet appearance of D1 is
also consistent with a simulated local dwarf hosting a SSC placed at z=6 and
lensed back to the observer. This compact system fits into some popular
globular cluster formation scenarios. We show that future high spatial
resolution imaging (e.g., E-ELT/MAORY-MICADO and VLT/MAVIS) will allow us to
spatially resolve light profiles of 2-8 pc.Comment: 21 pages, 14 figures, 1 table, MNRAS accepte
On the accuracy of time-delay cosmography in the Frontier Fields Cluster MACS J1149.5+2223 with supernova Refsdal
We study possible systematic effects on the values of the cosmological
parameters measured through strong lensing analyses of the HFF galaxy cluster
MACS J1149.5+2223. We use the observed positions of a large set of
spectroscopically selected multiple images, including those of supernova
"Refsdal" with their estimated time delays. Starting from our reference model
in a flat CDM cosmology, published in Grillo et al. (2018), we confirm
the relevance of the longest measurable time delay, between SX and S1, and an
approximately linear relation between its value and that of . We perform
true blind tests by considering a range of time delays around its original
estimate of days, as an accurate measurement of this time delay
was not known at the time of analysis and writing. We investigate separately
the impact of a constant sheet of mass at the cluster redshift, of a power-law
profile for the mass density of the cluster main halo and of some scatter in
the cluster member scaling relations. Remarkably, we find that these systematic
effects do not introduce a significant bias on the inferred values of
and and that the statistical uncertainties dominate the total
error budget: a 3% uncertainty on the time delay of image SX translates into
approximately 6% and 40% (including both statistical and systematic )
uncertainties for and , respectively. Furthermore, our
model accurately reproduces the extended surface brightness distribution of the
supernova host, covering more than pixels. We also
present the interesting possibility of measuring the value of the
equation-of-state parameter of the dark energy density, currently with a
30% uncertainty. We conclude that time-delay cluster lenses have the potential
to become soon an alternative and competitive cosmological probe.Comment: 10 pages, 8 figures, 1 table; ApJ in press (all main results and
figures unchanged, only minor changes during revision
CLASH-VLT: Environment-driven evolution of galaxies in the z=0.209 cluster Abell 209
The analysis of galaxy properties and the relations among them and the
environment, can be used to investigate the physical processes driving galaxy
evolution. We study the cluster A209 by using the CLASH-VLT spectroscopic data
combined with Subaru photometry, yielding to 1916 cluster members down to a
stellar mass of 10^{8.6} Msun. We determine: i) the stellar mass function of
star-forming and passive galaxies; ii) the intra-cluster light and its
properties; iii) the orbits of low- and high-mass passive galaxies; and iv) the
mass-size relation of ETGs. The stellar mass function of the star-forming
galaxies does not depend on the environment, while the slope found for passive
galaxies becomes flatter in the densest region. The color distribution of the
intra-cluster light is consistent with the color of passive members. The
analysis of the dynamical orbits shows that low-mass passive galaxies have
tangential orbits, avoiding small pericenters around the BCG. The mass-size
relation of low-mass passive ETGs is flatter than that of high mass galaxies,
and its slope is consistent with that of field star-forming galaxies. Low-mass
galaxies are also more compact within the scale radius of 0.65 Mpc. The ratio
between stellar and number density profiles shows a mass segregation in the
center. The comparative analysis of the stellar and total density profiles
indicates that this effect is due to dynamical friction. Our results are
consistent with a scenario in which the "environmental quenching" of low-mass
galaxies is due to mechanisms such as harassment out to R200, starvation and
ram-pressure stripping at smaller radii, as supported by the analysis of the
mass function, of the dynamical orbits and of the mass-size relation of passive
early-types in different regions. Our analyses support the idea that the
intra-cluster light is formed through the tidal disruption of subgiant
galaxies.Comment: 17 pages, 20 figures, A&A in pres
The story of supernova 'Refsdal' told by MUSE
We present MUSE observations in the core of the HFF galaxy cluster MACS
J1149.5+2223, where the first magnified and spatially-resolved multiple images
of SN 'Refsdal' at redshift 1.489 were detected. Thanks to a DDT program with
the VLT and the extraordinary efficiency of MUSE, we measure 117 secure
redshifts with just 4.8 hours of total integration time on a single target
pointing. We spectroscopically confirm 68 galaxy cluster members, with redshift
values ranging from 0.5272 to 0.5660, and 18 multiple images belonging to 7
background, lensed sources distributed in redshifts between 1.240 and 3.703.
Starting from the combination of our catalog with those obtained from extensive
spectroscopic and photometric campaigns using the HST, we select a sample of
300 (164 spectroscopic and 136 photometric) cluster members, within
approximately 500 kpc from the BCG, and a set of 88 reliable multiple images
associated to 10 different background source galaxies and 18 distinct knots in
the spiral galaxy hosting SN 'Refsdal'. We exploit this valuable information to
build 6 detailed strong lensing models, the best of which reproduces the
observed positions of the multiple images with a rms offset of only 0.26". We
use these models to quantify the statistical and systematic errors on the
predicted values of magnification and time delay of the next emerging image of
SN 'Refsdal'. We find that its peak luminosity should should occur between
March and June 2016, and should be approximately 20% fainter than the dimmest
(S4) of the previously detected images but above the detection limit of the
planned HST/WFC3 follow-up. We present our two-dimensional reconstruction of
the cluster mass density distribution and of the SN 'Refsdal' host galaxy
surface brightness distribution. We outline the roadmap towards even better
strong lensing models with a synergetic MUSE and HST effort.Comment: 21 pages, 9 figures, 6 tables; accepted for publication in the
Astrophysical Journal - extra information on data analysis added, all model
predictions and results unchange
Ionising the Intergalactic Medium by Star Clusters: The first empirical evidence
We present a VLT/X-Shooter spectroscopy of the Lyman continuum (LyC) emitting
galaxy 'Ion2' at z=3.2121 and compare it to that of the recently discovered
strongly lensed LyC-emitter at z=2.37, known as the 'Sunburst' arc. Three main
results emerge from the X-Shooter spectrum: (a) the Lya has three distinct
peaks with the central one at the systemic redshift, indicating a ionised
tunnel through which both Lya and LyC radiation escape; (b) the large O32
oxygen index ([OIII]4959-5007 / [OII]3727-3729) of 9.18(-1.32/+1.82) is
compatible to those measured in local (z~0.4) LyC leakers; (c) there are narrow
nebular high-ionisation metal lines with \sigma_v < 20 km/s, which confirms the
presence of young hot, massive stars. The HeII1640 appears broad, consistent
with a young stellar component including Wolf-Rayet stars. Similarly, the
Sunburst LyC-emitter shows a triple-peaked Lya profile and from VLT/MUSE
spectroscopy the presence of spectral features arising from young hot and
massive stars. The strong lensing magnification, (\mu > 20), suggests that this
exceptional object is a gravitationally-bound star cluster observed at a
cosmological distance, with a stellar mass M <~ 10^7 Msun and an effective
radius smaller than 20 pc. Intriguingly, sources like Sunburst but without
lensing magnification might appear as Ion2-like galaxies, in which unresolved
massive star clusters dominate the ultraviolet emission. This work supports the
idea that dense young star clusters can contribute to the ionisation of the IGM
through holes created by stellar feedback.Comment: 13 pages, 9 figures and 1 table, MNRAS accepted. Some typos fixe
CLASH-VLT: The inner slope of the MACS J1206.2-0847 mass density profile
The inner slope gammaDM of the dark matter (DM) density profile of
cosmological halos carries information about the properties of DM and/or
baryonic processes affecting the halo gravitational potential. Cold DM
cosmological simulations predict steep inner slopes, gammaDM>~1. We test this
prediction on the MACS J1206.2-0847 cluster at redshift z=0.44, whose DM
density profile was claimed to be cored at the center. We determine the cluster
DM density profile from 2 kpc from the cluster center to the virial radius (~2
Mpc), using the velocity distribution of ~500 cluster galaxies and the velocity
dispersion profile of the Brightest Cluster Galaxy (BCG), obtained from
VIMOS@VLT and MUSE@VLT data. We solve the Jeans equation of dynamical
equilibrium using an upgraded version of the MAMPOSSt method. The total mass
profile is modeled as a sum of a generalized-NFW profile that describes the DM
component, allowing for a free inner slope of the density profile, a Jaffe
profile that describes the BCG stellar mass component, and a non-parametric
baryonic profile that describes the sum of the remaining galaxy stellar mass
and of the hot intra-cluster gas mass. Our total mass profile is in remarkable
agreement with independent determinations based on X-ray observations and
strong lensing. We find gammaDM=0.7 -0.1 +0.2 (68% confidence levels),
consistent with predictions from recent LambdaCDM cosmological numerical
simulations.Comment: Submitted to ApJ on June, 1st 2023. 14 pages, 9 figure
Monorail/Foxa2 regulates floorplate differentiation and specification of oligodendrocytes, serotonergic raphe neurones and cranial motoneurones
In this study, we elucidate the roles of the winged-helix transcription factor Foxa2 in ventral CNS development in zebrafish. Through cloning of monorail (mol), which we find encodes the transcription factor Foxa2, and phenotypic analysis of mol(-/-) embryos, we show that floorplate is induced in the absence of Foxa2 function but fails to further differentiate. In mol(-/-) mutants, expression of Foxa and Hh family genes is not maintained in floorplate cells and lateral expansion of the floorplate fails to occur. Our results suggest that this is due to defects both in the regulation of Hh activity in medial floorplate cells as well as cell-autonomous requirements for Foxa2 in the prospective laterally positioned floorplate cells themselves. Foxa2 is also required for induction and/or patterning of several distinct cell types in the ventral CNS. Serotonergic neurones of the raphe nucleus and the trochlear motor nucleus are absent in mol(-/-) embryos, and oculomotor and facial motoneurones ectopically occupy ventral CNS midline positions in the midbrain and hindbrain. There is also a severe reduction of prospective oligodendrocytes in the midbrain and hindbrain. Finally, in the absence of Foxa2, at least two likely Hh pathway target genes are ectopically expressed in more dorsal regions of the midbrain and hindbrain ventricular neuroepithelium, raising the possibility that Foxa2 activity may normally be required to limit the range of action of secreted Hh proteins
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