57 research outputs found
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 Theoretical Astrophysical Observatory: Cloud-Based Mock Galaxy Catalogues
We introduce the Theoretical Astrophysical Observatory (TAO), an online
virtual laboratory that houses mock observations of galaxy survey data. Such
mocks have become an integral part of the modern analysis pipeline. However,
building them requires an expert knowledge of galaxy modelling and simulation
techniques, significant investment in software development, and access to high
performance computing. These requirements make it difficult for a small
research team or individual to quickly build a mock catalogue suited to their
needs. To address this TAO offers access to multiple cosmological simulations
and semi-analytic galaxy formation models from an intuitive and clean web
interface. Results can be funnelled through science modules and sent to a
dedicated supercomputer for further processing and manipulation. These modules
include the ability to (1) construct custom observer light-cones from the
simulation data cubes; (2) generate the stellar emission from star formation
histories, apply dust extinction, and compute absolute and/or apparent
magnitudes; and (3) produce mock images of the sky. All of TAO's features can
be accessed without any programming requirements. The modular nature of TAO
opens it up for further expansion in the future.Comment: 17 pages, 11 figures, 2 tables; accepted for publication in ApJS. The
Theoretical Astrophysical Observatory (TAO) is now open to the public at
https://tao.asvo.org.au/. New simulations, models and tools will be added as
they become available. Contact [email protected] if you have data you
would like to make public through TAO. Feedback and suggestions are very
welcom
Semi-Analytic Galaxy Evolution (SAGE): Model Calibration and Basic Results
This paper describes a new publicly available codebase for modelling galaxy
formation in a cosmological context, the "Semi-Analytic Galaxy Evolution"
model, or SAGE for short. SAGE is a significant update to that used in Croton
et al. (2006) and has been rebuilt to be modular and customisable. The model
will run on any N-body simulation whose trees are organised in a supported
format and contain a minimum set of basic halo properties. In this work we
present the baryonic prescriptions implemented in SAGE to describe the
formation and evolution of galaxies, and their calibration for three N-body
simulations: Millennium, Bolshoi, and GiggleZ. Updated physics include: gas
accretion, ejection due to feedback, and reincorporation via the galactic
fountain; a new gas cooling--radio mode active galactic nucleus (AGN) heating
cycle; AGN feedback in the quasar mode; a new treatment of gas in satellite
galaxies; and galaxy mergers, disruption, and the build-up of intra-cluster
stars. Throughout, we show the results of a common default parameterization on
each simulation, with a focus on the local galaxy population.Comment: 15 pages, 9 figures, accepted for publication in ApJS. SAGE is a
publicly available codebase for modelling galaxy formation in a cosmological
context, available at https://github.com/darrencroton/sage Questions and
comments can be sent to Darren Croton: [email protected]
Ly as a tracer of cosmic reionization in the SPHINX radiation-hydrodynamics cosmological simulation
The Ly emission line is one of the most promising probes of cosmic reionisation but isolating the signature of a change in the ionisation state of the IGM is challenging because of intrinsic evolution and internal radiation transfer effects. We present the first study of the evolution of Ly emitters (LAE) during the epoch of reionisation based on a full radiation-hydrodynamics cosmological simulation that is able to capture both the large-scale process of reionisation and the small-scale properties of galaxies. We predict the Ly emission of galaxies in the cMpc SPHINX simulation at by computing the full Ly radiation transfer from ISM to IGM scales. SPHINX is able to reproduce many observational constraints such as the UV/Ly luminosity functions and stellar mass functions at z 6 for the dynamical range probed by our simulation (, erg/s, M). As intrinsic Ly emission and internal Ly escape fractions barely evolve from to 9, the observed suppression of Ly luminosities with increasing redshift is fully attributed to IGM absorption. For most observable galaxies (), the Ly line profiles are slightly shifted to the red due to internal radiative transfer effects which mitigates the effect of IGM absorption. Overall, the enhanced Ly suppression during reionisation traces the IGM neutral fraction well but the predicted amplitude of this reduction is a strong function of the Ly peak shift, which is set at ISM/CGM scales. We find that a large number of LAEs could be detectable in very deep surveys during reionisation when is still
Simulating the diversity of shapes of the Lyman- line
The Ly line is a powerful probe of distant galaxies, which contains
information about inflowing/outflowing gas through which Ly photons
scatter. To develop our understanding of this probe, we post-process a zoom-in
radiation-hydrodynamics simulation of a low-mass ()
galaxy to construct 22500 mock spectra in 300 directions from to 4.
Remarkably, we show that one galaxy can reproduce the variety of a large sample
of spectroscopically observed Ly line profiles. While most mock spectra
exhibit double-peak profiles with a dominant red peak, their shapes cover a
large parameter space in terms of peak velocities, peak separation and flux
ratio. This diversity originates from radiative transfer effects at ISM and CGM
scales, and depends on galaxy inclination and evolutionary phase. Red-dominated
lines preferentially arise in face-on directions during post-starburst outflows
and are bright. Conversely, accretion phases usually yield symmetric double
peaks in the edge-on direction and are fainter. While resonant scattering
effects at are responsible for the broadening and
velocity shift of the red peak, the extended CGM acts as a screen and impacts
the observed peak separation. The ability of simulations to reproduce observed
Ly profiles and link their properties with galaxy physical parameters
offers new perspectives to use Ly to constrain the mechanisms that
regulate galaxy formation and evolution. Notably, our study implies that deeper
Ly surveys may unveil a new population of blue-dominated lines tracing
inflowing gas.Comment: Accepted for publication in MNRA
The MUSE-Wide survey: A measurement of the Ly emitting fraction among galaxies
We present a measurement of the fraction of Lyman (Ly)
emitters () amongst HST continuum-selected galaxies at
with the Multi-Unit Spectroscopic Explorer (MUSE) on the VLT. Making
use of the first 24 MUSE-Wide pointings in GOODS-South, each having an
integration time of 1 hour, we detect 100 Ly emitters and find
for most of the redshift range covered, with 29
per cent of the Ly sample exhibiting rest equivalent widths (rest-EWs)
15\AA. Adopting a range of rest-EW cuts (0 - 75\AA), we find no evidence
of a dependence of on either redshift or UV luminosity.Comment: 10 pages, 5 figures (MNRAS, updated as per version in press
The MUSE Hubble Ultra Deep Field Survey X. Ly Equivalent Widths at
We present rest-frame Ly equivalent widths (EW) of 417 Ly
emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the
Very Large Telescope (VLT) at in the Hubble Ultra Deep Field.
Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST)
photometry data, we carefully measured EW values taking into account extended
Ly emission and UV continuum slopes (). Our LAEs reach
unprecedented depths, both in Ly luminosities and UV absolute
magnitudes, from log(/erg s) 41.0 to 43.0 and
from Muv -16 to -21 (0.01-1.0 ). The EW values span the
range of 5 to 240 \AA\ or larger, and their distribution can be well
fitted by an exponential law exp(EW/). Owing to
the high dynamic range in Muv, we find that the scale factor, ,
depends on Muv in the sense that including fainter Muv objects increases
, i.e., the Ando effect. The results indicate that selection
functions affect the EW scale factor. Taking these effects into account, we
find that our values are consistent with those in the literature
within uncertainties at at a given threshold of Muv
and . Interestingly, we find 12 objects with EW \AA\
above uncertainties. Two of these 12 LAEs show signatures of merger
or AGN activity: the weak CIV emission line. For the remaining
10 very large EW LAEs, we find that the EW values can be reproduced by young
stellar ages ( Myr) and low metallicities ( ). Otherwise, at least part of the Ly emission in these LAEs
needs to arise from anisotropic radiative transfer effects, fluorescence by
hidden AGN or quasi-stellar object activity, or gravitational cooling.Comment: 22 pages, 12 figures, 9 tables, accepted for publication in A&A (MUSE
UDF Series Paper X
How to Quench a Dwarf Galaxy: The Impact of Inhomogeneous Reionization on Dwarf Galaxies and Cosmic Filaments
We use the SPHINX suite of high-resolution cosmological radiation
hydrodynamics simulations to study how spatially and temporally inhomogeneous
reionization impacts the baryonic content of dwarf galaxies and cosmic
filaments. The SPHINX simulations simultaneously capture the large-scale
process of reionization, model the escape of ionising radiation from thousands
of galaxies, and resolve haloes well below the atomic cooling threshold. This
makes them an ideal tool for examining how reionization impacts star formation
and the gas content of dwarf galaxies. We compare simulations with and without
stellar radiation to isolate the effects of radiation feedback from that of
supernova, cosmic expansion, and numerical resolution. We find that the gas
content of cosmic filaments can be reduced by more than 80% following
reionization. The gas inflow rates into haloes with
are strongly affected and are reduced by more
than an order of magnitude compared to the simulation without reionization. A
significant increase in gas outflow rates is found for halo masses
. Our simulations show that inflow
suppression (i.e. starvation), rather than photoevaporation, is the dominant
mechanism by which the baryonic content of high-redshift dwarf galaxies is
regulated. At fixed redshift and halo mass, there is a large scatter in the
halo baryon fractions that is entirely dictated by the timing of reionization
in the local region surrounding a halo. Finally, although the gas content of
high-redshift dwarf galaxies is significantly impacted by reionization, we find
that most haloes with can remain self-shielded
and form stars long after reionization, until their local gas reservoir is
depleted, suggesting that local group dwarf galaxies do not necessarily exhibit
star formation histories that peak prior to
Median Surface Brightness Profiles of Lyman- Haloes in the MUSE Extremely Deep Field
We present the median surface brightness profiles of diffuse Ly
haloes (LAHs) around star-forming galaxies by stacking 155 spectroscopically
confirmed Ly emitters (LAEs) at 3<z<4 in the MUSE Extremely Deep Field
(MXDF), with median Ly luminosity . After correcting for a systematic surface brightness
offset we identified in the datacube, we detect extended Ly emission
out to a distance of 270 kpc. The median Ly surface brightness profile
shows a power-law decrease in the inner 20 kpc, and a possible flattening trend
at larger distance. This shape is similar for LAEs with different Ly
luminosities, but the normalisation of the surface brightness profile increases
with luminosity. At distances larger than 50 kpc, we observe strong overlap of
adjacent LAHs, and the Ly surface brightness is dominated by the LAHs
of nearby LAEs. We find no clear evidence of redshift evolution of the observed
Ly profiles when comparing with samples at 4<z<5 and 5<z<6. Our results
are consistent with a scenario in which the inner 20 kpc of the LAH is powered
by star formation in the central galaxy, while the LAH beyond a radius of 50
kpc is dominated by photons from surrounding galaxies.Comment: Submitted to A&
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