55 research outputs found
Red nuggets grow inside-out: evidence from gravitational lensing
We present a new sample of strong gravitational lens systems where both the
foreground lenses and background sources are early-type galaxies. Using imaging
from HST/ACS and Keck/NIRC2, we model the surface brightness distributions and
show that the sources form a distinct population of massive, compact galaxies
at redshifts , lying systematically below the
size-mass relation of the global elliptical galaxy population at those
redshifts. These may therefore represent relics of high-redshift red nuggets or
their partly-evolved descendants. We exploit the magnifying effect of lensing
to investigate the structural properties, stellar masses and stellar
populations of these objects with a view to understanding their evolution. We
model these objects parametrically and find that they generally require two
S\'ersic components to properly describe their light profiles, with one more
spheroidal component alongside a more envelope-like component, which is
slightly more extended though still compact. This is consistent with the
hypothesis of the inside-out growth of these objects via minor mergers. We also
find that the sources can be characterised by red-to-blue colour gradients as a
function of radius which are stronger at low redshift -- indicative of ongoing
accretion -- but that their environments generally appear consistent with that
of the general elliptical galaxy population, contrary to recent suggestions
that these objects are predominantly associated with clusters.Comment: 21 pages; accepted for publication in MNRA
A Candidate Dual Active Galactic Nucleus At Z=1.175
The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Bootes field, shows double-peaked rest-frame optical/UV emission lines, separated by 0.''69 (5.5 kpc) in the spatial dimension and by 690 km s(-1) in the velocity dimension. The high excitation lines and emission line ratios indicate both systems are ionized by an active galactic nucleus (AGN) continuum, and the double-peaked profile resembles that of candidate dual AGNs. At a redshift of z = 1.175, this source is the highest redshift candidate dual AGN yet identified. However, many sources have similar emission line profiles for which other interpretations are favored. We have analyzed the substantial archival data available in this field as well as acquired near-infrared (NIR) adaptive optics (AO) imaging and NIR slit spectroscopy. The X-ray spectrum is hard, implying a column density of several 10(23) cm(-2). Though heavily obscured, the source is also one of the brightest in the field, with an absorption-corrected 2-10 keV luminosity of similar to 10(45) erg s(-1). Outflows driven by an accretion disk may produce the double-peaked lines if the central engine accretes near the Eddington limit. However, we may be seeing the narrow line regions of two AGNs following a galactic merger. While the AO image reveals only a single source, a second AGN would easily be obscured by the significant extinction inferred from the X-ray data. Understanding the physical processes producing the complex emission line profiles seen in CXOJ1426+35 and related sources is important for interpreting the growing population of dual AGN candidates.National Science Foundation AST-0708490Strategic University Research Partnership ProgramNational Aeronautics and Space AdministrationW. M. Keck FoundationSmithsonian Astrophysical Observatory SV4-74018, A31Astronom
3C 220.3: a radio galaxy lensing a submillimeter galaxy
Herschel Space Observatory photometry and extensive multiwavelength followup
have revealed that the powerful radio galaxy 3C 220.3 at z=0.685 acts as a
gravitational lens for a background submillimeter galaxy (SMG) at z=2.221. At
an observed wavelength of 1mm, the SMG is lensed into three distinct images. In
the observed near infrared, these images are connected by an arc of 1.8" radius
forming an Einstein half-ring centered near the radio galaxy. In visible light,
only the arc is apparent. 3C 220.3 is the only known instance of strong
galaxy-scale lensing by a powerful radio galaxy not located in a galaxy cluster
and therefore it offers the potential to probe the dark matter content of the
radio galaxy host. Lens modeling rejects a single lens, but two lenses centered
on the radio galaxy host A and a companion B, separated by 1.5", provide a fit
consistent with all data and reveal faint candidates for the predicted fourth
and fifth images. The model does not require an extended common dark matter
halo, consistent with the absence of extended bright X-ray emission on our
Chandra image. The projected dark matter fractions within the Einstein radii of
A (1.02") and B (0.61") are about 0.4 +/- 0.3 and 0.55 +/- 0.3. The mass to
i-band light ratios of A and B, M/L ~ 8 +/- 4 Msun/Lsun, appear comparable to
those of radio-quiet lensing galaxies at the same redshift in the CASTLES, LSD,
and SL2S samples. The lensed SMG is extremely bright with observed f(250um) =
440mJy owing to a magnification factor mu~10. The SMG spectrum shows luminous,
narrow CIV 154.9nm emission, revealing that the SMG houses a hidden quasar in
addition to a violent starburst. Multicolor image reconstruction of the SMG
indicates a bipolar morphology of the emitted ultraviolet (UV) light suggestive
of cones through which UV light escapes a dust-enshrouded nucleus.Comment: 17 pages, 14 Figures, accepted for publication in Ap
Joint HST, VLT/MUSE and XMM-Newton observations to constrain the mass distribution of the two strong lensing galaxy clusters: MACS J0242.5-2132 & MACS J0949.8+1708
We present the strong lensing analysis of two galaxy clusters: MACS
J0242.5-2132 (MACS J0242, ) and MACS J0949.8+1708 (MACS J0949,
). Their total matter distributions are constrained thanks to the
powerful combination of observations with the Hubble Space Telescope and the
MUSE instrument. Using these observations, we precisely measure the redshift of
six multiple image systems in MACS J0242, and two in MACS J0949. We also
include four multiple image systems in the latter cluster identified in HST
imaging without MUSE redshift measurements. For each cluster, our best-fit mass
model consists of a single cluster-scale halo, and 57 (170) galaxy-scale halos
for MACS J0242 (MACS J0949). Multiple images positions are predicted with a
0.39 arcsec and 0.15 arcsec for MACS J0242 and MACS J0949 models
respectively. From these mass models, we derive aperture masses of 200
kpc, and 200 kpc. Combining our analysis with
X-ray observations from the XMM-Newton Observatory, we show that MACS J0242
appears to be a relatively relaxed cluster, while conversely, MACS J0949 shows
a relaxing post-merger state. At 200 kpc, X-ray observations suggest the hot
gas fraction to be respectively and
for MACS J0242 and MACS J0949. MACS J0242 being
relaxed, its density profile is very well fitted by a NFW distribution, in
agreement with X-ray observations. Finally, the strong lensing analysis of MACS
J0949 suggests a flat dark matter density distribution in the core, between 10
and 100 kpc. This appears consistent with X-ray observations.Comment: 20 pages, 11 figures, published in MNRA
A full reconstruction of two galaxy clusters intra-cluster medium with strong gravitational lensing
Whilst X-rays and Sunyaev-Zel'dovich observations allow to study the
properties of the intra-cluster medium (ICM) of galaxy clusters, their
gravitational potential may be constrained using strong gravitational lensing.
Although being physically related, these two components are often described
with different physical models. Here, we present a unified technique to derive
the ICM properties from strong lensing for clusters in hydrostatic equilibrium.
In order to derive this model, we present a new universal and self-similar
polytropic temperature profile, which we fit using the X-COP sample of
clusters. We subsequently derive an analytical model for the electron density,
which we apply to strong lensing clusters MACS J0242.5-2132 and MACS
J0949.8+1708. We confront the inferred ICM reconstructions to XMM-Newton and
ACT observations. We contrast our analytical electron density reconstructions
with the best canonical -model. The ICM reconstructions obtained prove
to be compatible with observations. However they appear to be very sensitive to
various dark matter halo parameters constrained through strong lensing (such as
the core radius), and to the halo scale radius (fixed in the lensing
optimisations). With respect to the important baryonic effects, we make the
sensitivity on the scale radius of the reconstruction an asset, and use the
inferred potential to constrain the dark matter density profile using ICM
observations. The technique here developed should allow to take a new, and more
holistic path to constrain the content of galaxy clusters.Comment: 26 pages, 21 figures, submitted to MNRA
Beyond the bulgeâhalo conspiracy? Density profiles of early-type galaxies from extended-source strong lensing
Observations suggest that the dark matter and stars in early-type galaxies âconspireâ to produce a surprisingly simple distribution of total mass, Ï(r) â ÏâÎł, with Îł â 2. We measure the distribution of mass in 48 early-type galaxies that gravitationally lens a resolved background source. By fitting the source light in every pixel of images from the Hubble Space Telescope, we find a mean âšÎłâ©=2.075+0.023â0.024 with an intrinsic scatter between galaxies of ÏÎł=0.172+0.022â0.032 for the overall sample. This is consistent with and has similar precision to traditional techniques that employ spectroscopic observations to supplement lensing with mass estimates from stellar dynamics. Comparing measurements of Îł for individual lenses using both techniques, we find a statistically insignificant correlation of â0.150+0.223â0.217 between the two, indicating a lack of statistical power or deviations from a power-law density in certain lenses. At fixed surface mass density, we measure a redshift dependence, ââšÎłâ©/z=0.345+0.322â0.296â , that is consistent with traditional techniques for the same sample of Sloan Lens ACS and GALaxy-Lyα EmitteR sYstems (GALLERY) lenses. Interestingly, the consistency breaks down when we measure the dependence of Îł on the surface mass density of a lens galaxy. We argue that this is tentative evidence for an inflection point in the total mass-density profile at a few times the galaxy effective radius â breaking the conspiracy
The Density Profiles of Massive, Relaxed Galaxy Clusters. II. Separating Luminous and Dark Matter in Cluster Cores
We present stellar and dark matter (DM) density profiles for a sample of
seven massive, relaxed galaxy clusters derived from strong and weak
gravitational lensing and resolved stellar kinematic observations within the
centrally-located brightest cluster galaxies (BCGs). In Paper I of the series,
we demonstrated that the total density profile derived from these data, which
span 3 decades in radius, is consistent with numerical DM-only simulations at
radii >~ 5-10 kpc, despite the significant contribution of stellar material in
the core. Here we decompose the inner mass profiles of these clusters into
stellar and dark components. Parametrizing the DM density profile as a power
law rho_DM ~ r^{-\beta} on small scales, we find a mean slope = 0.50 +-
0.10 (random) +0.14-0.13 (systematic). Alternatively, cored Navarro-Frenk-White
(NFW) profiles with = 1.14 +- 0.13 (random) +0.14-0.22
(systematic) provide an equally good description. These density profiles are
significantly shallower than canonical NFW models at radii <~ 30 kpc,
comparable to the effective radii of the BCGs. The inner DM profile is
correlated with the distribution of stars in the BCG, suggesting a connection
between the inner halo and the assembly of stars in the central galaxy. The
stellar mass-to-light ratio inferred from lensing and stellar dynamics is
consistent with that inferred using stellar population synthesis models if a
Salpeter initial mass function is adopted. We compare these results to theories
describing the interaction between baryons and DM in cluster cores, including
adiabatic contraction models and the possible effects of galaxy mergers and
active galactic nucleus feedback, and evaluate possible signatures of
alternative DM candidates.Comment: Updated to matched the published version in Ap
Probing the faint end Luminosity Function of Lyman Alpha Emitters at 3<z<7 behind 17 MUSE lensing clusters
We present a study of the galaxy Lyman-alpha luminosity function (LF) using a
sample of 17 lensing clusters observed by the MUSE/VLT. Magnification from
strong gravitational lensing by clusters of galaxies and MUSE apabilities allow
us to blindly detect LAEs without any photometric pre-selection, reaching the
faint luminosity regime. 600 lensed LAEs were selected behind these clusters in
the redshift range 2.9<< 6.7, covering four orders of magnitude in
magnification-corrected Lyman-alpha luminosity (39.0<log< 43.0). The method
used in this work () follows the recipes originally developed
by arXiv:1905.13696(N) (DLV19) with some improvements to better account for the
effects of lensing when computing the effective volume. The total co-moving
volume at 2.9<<6.7 is 50 . Our LF points in the bright
end (log L)>42 are consistent with those obtained from blank field
observations. In the faint luminosity regime, the density of sources is well
described by a steep slope, for the global redshift range. Up to
log(L)41, the steepening of the faint end slope with redshift, suggested
by the earlier work of DLV19 is observed, but the uncertainties remain large. A
significant flattening is observed towards the faintest end, for the highest
redshift bins (log<41). Using face values, the steep slope at the faint-end
causes the SFRD to dramatically increase with redshift, implying that LAEs
could play a major role in the process of cosmic reionization. The flattening
observed towards the faint end for the highest redshift bins still needs
further investigation. This turnover is similar to the one observed for the UV
LF at in lensing clusters, with the same conclusions regarding the
reliability of current results (e.g.arXiv:1803.09747(N); arXiv:2205.11526(N)).Comment: 20 pages, 15 figures, 6 tables. Accepted for publication in A\&
Pilot-WINGS: An extended MUSE view of the structure of Abell 370
We investigate the strong-lensing cluster Abell 370 (A370) using a wide Integral Field Unit (IFU) spectroscopic mosaic from the Multi-Unit Spectroscopic Explorer (MUSE). IFU spectroscopy provides significant insight into the structure and mass content of galaxy clusters, yet IFU-based cluster studies focus almost exclusively on the central Einstein-radius region. Covering over 14 arcmin2, the new MUSE mosaic extends significantly beyond the A370 Einstein radius, providing, for the first time, a detailed look at the cluster outskirts. Combining these data with wide-field, multi-band Hubble Space Telescope (HST) imaging from the BUFFALO project, we analyse the distribution of objects within the cluster and along the line of sight. Identifying 416 cluster galaxies, we use kinematics to trace the radial mass profile of the halo, providing a mass estimate independent from the lens model. We also measure radially averaged properties of the cluster members, tracking their evolution as a function of infall. Thanks to the high spatial resolution of our data, we identify six cluster members acting as galaxyâgalaxy lenses, which constrain localized mass distributions beyond the Einstein radius. Finally, taking advantage of MUSEâs 3D capabilities, we detect and analyse multiple spatially extended overdensities outside of the cluster that influence lensing-derived halo mass estimates. We stress that much of this work is only possible thanks to the robust, extended IFU coverage, highlighting its importance even in less optically dense cluster regions. Overall, this work showcases the power of combining HST + MUSE, and serves as the initial step towards a larger and wider program targeting several clusters
SHARDS frontier fields: physical properties of a low-mass Lyα emitter at z = 5.75
We analyze the properties of a multiply-imaged Lyman-alpha (Lya) emitter at
z=5.75 identified through SHARDS Frontier Fields intermediate-band imaging of
the Hubble Frontier Fields (HFF) cluster Abell 370. The source, A370-L57, has
low intrinsic luminosity (M_UV~-16.5), steep UV spectral index
(\beta=-2.4+/-0.1), and extreme rest-frame equivalent width of Lya
(EW(Lya)=420+180-120 \AA). Two different gravitational lens models predict high
magnification (\mu~10--16) for the two detected counter-images, separated by
7", while a predicted third counter-image (\mu~3--4) is undetected. We find
differences of ~50% in magnification between the two lens models, quantifying
our current systematic uncertainties. Integral field spectroscopy of A370-L57
with MUSE shows a narrow (FWHM=204+/-10 km/s) and asymmetric Lya profile with
an integrated luminosity L(Lya)~10^42 erg/s. The morphology in the HST bands
comprises a compact clump (r_e<100 pc) that dominates the Lya and continuum
emission and several fainter clumps at projected distances <1 kpc that coincide
with an extension of the Lya emission in the SHARDS F823W17 and MUSE
observations. The latter could be part of the same galaxy or an interacting
companion. We find no evidence of contribution from AGN to the Lya emission.
Fitting of the spectral energy distribution with stellar population models
favors a very young (t<10 Myr), low mass (M*~10^6.5 Msun), and metal poor
(Z<4x10^-3) stellar population. Its modest star formation rate (SFR~1.0
Msun/yr) implies high specific SFR (sSFR~2.5x10^-7 yr^-1) and SFR density
(Sigma_SFR ~ 7-35 Msun/yr/kpc^2). The properties of A370-L57 make it a good
representative of the population of galaxies responsible for cosmic
reionization.Comment: 14 pages, 8 figures, 4 tables. Accepted for publication in Ap
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