11,820 research outputs found
The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817
The historic detection of gravitational waves from a binary neutron star
merger (GW170817) and its electromagnetic counterpart led to the first accurate
(sub-arcsecond) localization of a gravitational-wave event. The transient was
found to be 10" from the nucleus of the S0 galaxy NGC 4993. We report
here the luminosity distance to this galaxy using two independent methods. (1)
Based on our MUSE/VLT measurement of the heliocentric redshift () we infer the systemic recession velocity of the
NGC 4993 group of galaxies in the cosmic microwave background (CMB) frame to be
km s. Using constrained cosmological
simulations we estimate the line-of-sight peculiar velocity to be km s, resulting in a cosmic velocity of km s () and a
distance of Mpc assuming a local Hubble constant of
km s Mpc. (2) Using Hubble Space Telescope
measurements of the effective radius (15.5" 1.5") and contained intensity
and MUSE/VLT measurements of the velocity dispersion, we place NGC 4993 on the
Fundamental Plane (FP) of E and S0 galaxies. Comparing to a frame of 10
clusters containing 226 galaxies, this yields a distance estimate of Mpc. The combined redshift and FP distance is Mpc. This 'electromagnetic' distance estimate is consistent
with the independent measurement of the distance to GW170817 as obtained from
the gravitational-wave signal ( Mpc) and
confirms that GW170817 occurred in NGC 4993.Comment: 9 pages, 5 figure
Prospects for Observing the low-density Cosmic Web in Lyman-alpha Emission
Mapping the intergalactic medium (IGM) in Lyman- emission would yield
unprecedented tomographic information on the large-scale distribution of
baryons and potentially provide new constraints on the UV background and
various feedback processes relevant to galaxy formation. Here, we use a
cosmological hydrodynamical simulation to examine the Lyman- emission
of the IGM due to collisional excitations and recombinations in the presence of
a UV background. We focus on gas in large-scale-structure filaments in which
Lyman- radiative transfer effects are expected to be moderate. At low
density the emission is primarily due to fluorescent re-emission of the
ionising UV background due to recombinations, while collisional excitations
dominate at higher densities. We discuss prospects of current and future
observational facilities to detect this emission and find that the emission of
filaments of the cosmic web will typically be dominated by the halos and
galaxies embedded in them, rather than by the lower density filament gas
outside halos. Detecting filament gas directly would require a very long
exposure with a MUSE-like instrument on the ELT. Our most robust predictions
that act as lower limits indicate this would be slightly less challenging at
lower redshifts (). We also find that there is a large amount of
variance between fields in our mock observations. High-redshift protoclusters
appear to be the most promising environment to observe the filamentary IGM in
Lyman- emission.Comment: 20 pages, 13 figures. Accepted for publication in Astronomy &
Astrophysics. Accepted version contains several revisions following
suggestions made in the review proces
Lyman-\alpha{} Emitters in the context of hierarchical galaxy formation: predictions for VLT/MUSE surveys
The VLT Multi Unit Spectroscopic Explorer (MUSE) integral-field spectrograph
can detect Ly\alpha{} emitters (LAE) in the redshift range in a homogeneous way. Ongoing MUSE surveys will notably probe
faint Ly\alpha{} sources that are usually missed by current narrow-band
surveys. We provide quantitative predictions for a typical wedding-cake
observing strategy with MUSE based on mock catalogs generated with a
semi-analytic model of galaxy formation coupled to numerical Ly\alpha{}
radiation transfer models in gas outflows. We expect 1500 bright LAEs
( erg s cm) in a typical
Shallow Field (SF) survey carried over 100 arcmin, and
2,000 sources as faint as erg s cm in a Medium-Deep
Field (MDF) survey over 10 arcmin. In a typical Deep Field (DF) survey of 1
arcmin, we predict that 500 extremely faint LAEs (
erg s cm) will be found. Our
results suggest that faint Ly\alpha{} sources contribute significantly to the
cosmic Ly\alpha{} luminosity and SFR budget. While the host halos of bright
LAEs at z 3 and 6 have descendants with median masses of and respectively, the faintest sources
detectable by MUSE at these redshifts are predicted to reside in halos which
evolve into typical sub- and galaxy halos at z = 0. We expect
typical DF and MDF surveys to uncover the building blocks of Milky Way-like
objects, even probing the bulk of the stellar mass content of LAEs located in
their progenitor halos at z 3.Comment: 18 pages, 13 figures, accepted for publication in MNRA
The Cosmic Ultraviolet Baryon Survey (CUBS) I. Overview and the diverse environments of Lyman limit systems at z<1
We present initial results from the Cosmic Ultraviolet Baryon Survey (CUBS).
CUBS is designed to map diffuse baryonic structures at redshift z<~1 using
absorption-line spectroscopy of 15 UV-bright QSOs with matching deep galaxy
survey data. CUBS QSOs are selected based on their NUV brightness to avoid
biases against the presence of intervening Lyman Limit Systems (LLSs) at
zabs~ 17.2 over a total
redshift survey pathlength of dz=9.3, and a number density of n(z)=0.43 (-0.18,
+0.26). Considering all absorbers with log N(HI)/cm^-2 > 16.5 leads to
n(z)=1.08 (-0.25, +0.31) at z<1. All LLSs exhibit a multi-component structure
and associated metal transitions from multiple ionization states such as CII,
CIII, MgII, SiII, SiIII, and OVI absorption. Differential chemical enrichment
levels as well as ionization states are directly observed across individual
components in three LLSs. We present deep galaxy survey data obtained using the
VLT-MUSE integral field spectrograph and the Magellan Telescopes, reaching
sensitivities necessary for detecting galaxies fainter than 0.1L* at d<~300
physical kpc (pkpc) in all five fields. A diverse range of galaxy properties is
seen around these LLSs, from a low-mass dwarf galaxy pair, a co-rotating
gaseous halo/disk, a star-forming galaxy, a massive quiescent galaxy, to a
galaxy group. The closest galaxies have projected distances ranging from d=15
to 72 pkpc and intrinsic luminosities from ~0.01L* to ~3L*. Our study shows
that LLSs originate in a variety of galaxy environments and trace gaseous
structures with a broad range of metallicities.Comment: 26 pages, 14 figures, MNRAS in pres
Strongly Time-Variable Ultra-Violet Metal Line Emission from the Circum-Galactic Medium of High-Redshift Galaxies
We use cosmological simulations from the Feedback In Realistic Environments
(FIRE) project, which implement a comprehensive set of stellar feedback
processes, to study ultra-violet (UV) metal line emission from the
circum-galactic medium of high-redshift (z=2-4) galaxies. Our simulations cover
the halo mass range Mh ~ 2x10^11 - 8.5x10^12 Msun at z=2, representative of
Lyman break galaxies. Of the transitions we analyze, the low-ionization C III
(977 A) and Si III (1207 A) emission lines are the most luminous, with C IV
(1548 A) and Si IV (1394 A) also showing interesting spatially-extended
structures. The more massive halos are on average more UV-luminous. The UV
metal line emission from galactic halos in our simulations arises primarily
from collisionally ionized gas and is strongly time variable, with
peak-to-trough variations of up to ~2 dex. The peaks of UV metal line
luminosity correspond closely to massive and energetic mass outflow events,
which follow bursts of star formation and inject sufficient energy into
galactic halos to power the metal line emission. The strong time variability
implies that even some relatively low-mass halos may be detectable. Conversely,
flux-limited samples will be biased toward halos whose central galaxy has
recently experienced a strong burst of star formation. Spatially-extended UV
metal line emission around high-redshift galaxies should be detectable by
current and upcoming integral field spectrographs such as the Multi Unit
Spectroscopic Explorer (MUSE) on the Very Large Telescope and Keck Cosmic Web
Imager (KCWI).Comment: 16 pages, 8 figures, accepted for publication in MNRA
The MURALES survey II. Presentation of MUSE observations of 20 3C low-z radio galaxies and first results
We present observations of a complete sub-sample of 20 radio galaxies from
the Third Cambridge Catalog (3C) with redshift <0.3 obtained from VLT/MUSE
optical integral field spectrograph. These data have been obtained as part of
the survey MURALES (a MUse RAdio Loud Emission line Snapshot survey) with the
main goal of exploring the Active Galactic Nuclei (AGN) feedback process in a
sizeable sample of the most powerful radio sources at low redshift. We present
the data analysis and, for each source, the resulting emission line images and
the 2D gas velocity field. Thanks to their unprecedented depth (the median 3
sigma surface brightness limit in the emission line maps is 6X10^-18 erg s-1
cm-2 arcsec-2, these observations reveal emission line structures extending to
several tens of kiloparsec in most objects. In nine sources the gas velocity
shows ordered rotation, but in the other cases it is highly complex. 3C sources
show a connection between radio morphology and emission line properties.
Whereas, in three of the four Fanaroff and Riley Class I radio galaxies (FRIs),
the line emission regions are compact, ~1 kpc in size; in all but one of the
Class II radiogalaxies FRIIs, we detected large scale structures of ionized gas
with a median extent of 17 kpc. Among the FRIIs, those of high and low
excitation show extended gas structures with similar morphological properties,
suggesting that they both inhabit regions characterized by a rich gaseous
environment on kpc scale.Comment: Accepted for publication in A&
Ubiquitous giant Ly nebulae around the brightest quasars at revealed with MUSE
Direct Ly imaging of intergalactic gas at has recently
revealed giant cosmological structures around quasars, e.g. the Slug Nebula
(Cantalupo et al. 2014). Despite their high luminosity, the detection rate of
such systems in narrow-band and spectroscopic surveys is less than 10%,
possibly encoding crucial information on the distribution of gas around quasars
and the quasar emission properties. In this study, we use the MUSE
integral-field instrument to perform a blind survey for giant Ly
nebulae around 17 bright radio-quiet quasars at that does not suffer
from most of the limitations of previous surveys. After data reduction and
analysis performed with specifically developed tools, we found that each quasar
is surrounded by giant Ly nebulae with projected sizes larger than 100
physical kpc and, in some cases, extending up to 320 kpc. The circularly
averaged surface brightness profiles of the nebulae appear very similar to each
other despite their different morphologies and are consistent with power laws
with slopes . The similarity between the properties of all these
nebulae and the Slug Nebula suggests a similar origin for all systems and that
a large fraction of gas around bright quasars could be in a relatively "cold"
(T10K) and dense phase. In addition, our results imply that such gas
is ubiquitous within at least 50 kpc from bright quasars at
independently of the quasar emission opening angle, or extending up to 200 kpc
for quasar isotropic emission.Comment: 19 pages, 9 figures, 3 Tables, accepted to Ap
GASP. XVI. Does cosmic web enhancement turn on star formation in galaxies?
Galaxy filaments are a peculiar environment, and their impact on the galaxy
properties is still controversial. Exploiting the data from the GAs Stripping
Phenomena in galaxies with MUSE (GASP), we provide the first characterisation
of the spatially resolved properties of galaxies embedded in filaments in the
local Universe. The four galaxies we focus on show peculiar ionised gas
distributions: Halpha clouds have been observed beyond four times the effective
radius. The gas kinematics, metallicity map and the ratios of emission line
fluxes confirm that they do belong to the galaxy gas disk, the analysis of
their spectra shows that very weak stellar continuum is associated to them.
Similarly, the star formation history and luminosity weighted age maps point to
a recent formation of such clouds. The clouds are powered by star formation,
and are characterised by intermediate values of dust absorption. We hypothesise
a scenario in which the observed features are due to "Cosmic Web Enhancement":
we are most likely witnessing galaxies passing through or flowing within
filaments that assist the gas cooling and increase the extent of the star
formation in the densest regions in the circumgalactic gas. Targeted
simulations are mandatory to better understand this phenomenon.Comment: MNRAS in press, 18 pages, 12 figure
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