7 research outputs found
FORECAST: a flexible software to forward model cosmological hydrodynamical simulations mimicking real observations
We present FORECAST, a new flexible and adaptable software package that
performs forward modeling of the output of any cosmological hydrodynamical
simulations to create a wide range of realistic synthetic astronomical images.
With customizable options for filters, field of view size and survey
parameters, it allows users to tailor the synthetic images to their specific
requirements. FORECAST constructs light-cone exploiting the output snapshots of
a simulation and computes the observed flux of each simulated stellar element,
modeled as a Single Stellar Population, in any chosen set of pass-band filters,
including k-correction, IGM absorption and dust attenuation. As a first
application, we emulated the GOODS-South field as observed for the CANDELS
survey exploiting the IllustrisTNG simulation. We produce images of 200 sq.
arcmin., in 13 bands (eight Hubble Space Telescope optical and near-infrared
bands from ACS B435 to WFC3 H160, the VLT HAWK-I Ks band, and the four IRAC
filters from Spitzer), with depths consistent with the real data. We analysed
the images with the same processing pipeline adopted for real data in CANDELS
and ASTRODEEP publications, and we compared the results against both the input
data used to create the images, and real data, generally finding good agreement
with both, with some interesting exceptions which we discuss. As part of this
work, we release the FORECAST code and two datasets: the CANDELS dataset
analyzed in this study, and 10 JWST CEERS survey-like images (8 NIRCam and 2
MIRI) in a field of view of 200 sq. arcmin. between z=0-20. FORECAST is a
flexible tool: it creates images that can then be processed and analysed using
standard photometric algorithms, allowing for a consistent comparison among
observations and models, and for a direct estimation of the biases introduced
by such techniques.Comment: 21 pages, 15 figures, 6 tables, submitted to A&
First Light And Reionisation Epoch Simulations (FLARES) VIII. The Emergence of Passive Galaxies at
Passive galaxies are ubiquitous in the local universe, and various physical
channels have been proposed that lead to this passivity. To date, robust
passive galaxy candidates have been detected up to , but it is
still unknown if they exist at higher redshifts, what their relative abundances
are, and what causes them to stop forming stars. We present predictions from
the First Light And Reionisation Epoch Simulations (FLARES), a series of zoom
simulations of a range of overdensities using the EAGLE code. Passive galaxies
occur naturally in the EAGLE model at high redshift, and are in good agreement
with number density estimates from HST and early JWST results at . Due to the unique FLARES approach, we extend these predictions to
higher redshifts, finding passive galaxy populations up to . Feedback
from supermassive black holes is the main driver of passivity, leading to
reduced gas fractions and star forming gas reservoirs. We find that passive
galaxies at are not identified in the typical UVJ selection
space due to their still relatively young stellar populations, and present new
rest--frame selection regions. We also present NIRCam and MIRI fluxes, and find
that significant numbers of passive galaxies at should be
detectable in upcoming wide surveys with JWST. Finally, we present JWST colour
distributions, with new selection regions in the observer--frame for
identifying these early passive populations.Comment: 21 pages, 20 figures. Accepted to MNRA
Cosmic Evolution Early Release Science (CEERS) survey: The colour evolution of galaxies in the distant Universe
The wavelength-coverage and sensitivity of JWST now enables us to probe the
rest-frame UV - optical spectral energy distributions (SEDs) of galaxies at
high-redshift (). From these SEDs it is, in principle, through SED fitting
possible to infer key physical properties, including stellar masses, star
formation rates, and dust attenuation. These in turn can be compared with the
predictions of galaxy formation simulations allowing us to validate and refine
the incorporated physics. However, the inference of physical properties,
particularly from photometry alone, can lead to large uncertainties and
potential biases. Instead, it is now possible, and common, for simulations to
be \emph{forward-modelled} to yield synthetic observations that can be compared
directly to real observations. In this work, we measure the JWST broadband
fluxes and colours of a robust sample of galaxies using the Cosmic
Evolution Early Release Science (CEERS) Survey. We then analyse predictions
from a variety of models using the same methodology and compare the
NIRCam/F277W magnitude distribution and NIRCam colours with observations. We
find that the predicted and observed magnitude distributions are similar, at
least at the distributions differ somewhat, though our
observed sample size is small and thus susceptible to statistical fluctuations.
Likewise, the predicted and observed colour evolution show broad agreement, at
least at . There is however some disagreement between the observed and
modelled strength of the strong line contribution. In particular all the models
fails to reproduce the F410M-F444W colour at , though, again, the sample
size is small here.Comment: 11 pages, 10 figures, submitted to MNRA
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
FORECAST: A flexible software to forward model cosmological hydrodynamical simulations mimicking real observations
Context. Comparing theoretical predictions to real data is crucial to properly formulate galaxy formation theories. However, this is usually done naively considering the direct output of simulations and quantities inferred from observations, which can lead to severe inconsistencies.
Aims. We present FORECAST, a new flexible and adaptable software package that performs forward modeling of the output of any cosmological hydrodynamical simulations to create a wide range of realistic synthetic astronomical images, and thus providing a robust foundation for accurate comparison with observational data. With customizable options for filters, field-of-view size, and survey parameters, it allows users to tailor the synthetic images to their specific requirements.
Methods. FORECAST constructs a light cone centered on the observer’s position exploiting the output snapshots of a simulation and computes the observed flux of each simulated stellar element, modeled as a single stellar population, in any chosen set of passband filters, including k correction, intergalactic medium absorption, and dust attenuation. These fluxes are then used to create an image on a grid of pixels, to which observational features such as background noise and PSF blurring can be added. This allows simulated galaxies to be obtained with realistic morphologies and star formation histories.
Results. As a first application, we present a set of images obtained exploiting the ILLUSTRI
First light and reionisation epoch simulations (FLARES) – VIII. The emergence of passive galaxies at z ≥ 5
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First light and reionisation epoch simulations (FLARES) - VIII. The emergence of passive galaxies at z ≥ 5
Passive galaxies are ubiquitous in the local universe, and various physical channels have been proposed that lead to this passivity. To date, robust passive galaxy candidates have been detected up to z ≤ 5, but it is still unknown if they exist at higher redshifts, what their relative abundances are, and what causes them to stop forming stars. We present predictions from the first light and reionisation epoch simulations (flares), a series of zoom simulations of a range of overdensities using the eagle code. Passive galaxies occur naturally in the eagle model at high redshift, and are in good agreement with number density estimates from Hubble Space Telescope (HST) and early JWST results at 3 ≤ z ≤ 5. Due to the unique flares approach, we extend these predictions to higher redshifts, finding passive galaxy populations up to z ∼8. Feedback from supermassive black holes is the main driver of passivity, leading to reduced gas fractions and star forming gas reservoirs. We find that passive galaxies at z ≥ 5 are not identified in the typical UVJ selection space due to their still relatively young stellar populations, and present new rest-frame selection regions. We also produce mock NIRCam and MIRI fluxes, and find that significant numbers of passive galaxies at z ≥ 5 should be detectable in upcoming wide surveys with JWST. Finally, we present JWST colour distributions, with new selection regions in the observer-frame for identifying these early passive populations.</p