468 research outputs found
Wildlife tourism in Scotland – the example of grouse shooting
Wildlife tourism in Scotland has seen a recent increase in profile, with two reports providing new figures on the economic value of the activity. The reports, by the Scottish Government and Scottish Natural Heritage (SNH), seem likely to generate policy responses to further develop the sector
A Public Ks-selected Catalog in the COSMOS/UltraVISTA Field: Photometry, Photometric Redshifts and Stellar Population Parameters
We present a catalog covering 1.62 deg^2 of the COSMOS/UltraVISTA field with
PSF-matched photometry in 30 photometric bands. The catalog covers the
wavelength range 0.15um - 24um including the available GALEX, Subaru, CFHT,
VISTA and Spitzer data. Catalog sources have been selected from the DR1
UltraVISTA Ks band imaging that reaches a depth of K_{s,tot} = 23.4 AB (90%
completeness). The PSF-matched catalog is generated using position-dependent
PSFs ensuring accurate colors across the entire field. Also included is a
catalog of photometric redshifts (z_phot) for all galaxies computed with the
EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample
shows that up to z ~ 1.5 the z_phot are accurate to dz/(1 + z) = 0.013, with a
catastrophic outlier fraction of only 1.6%. The z_phot also show good agreement
with the z_phot from the NEWFIRM Medium Band Survey (NMBS) out to z ~ 3. A
catalog of stellar masses and stellar population parameters for galaxies
determined using the FAST spectral energy distribution fitting code is provided
for all galaxies. Also included are rest-frame U-V and V-J colors, L_2800 and
L_IR. The UVJ color-color diagram confirms that the galaxy bi-modality is
well-established out to z ~ 2. Star-forming galaxies also obey a star forming
"main sequence" out to z ~ 2.5, and this sequence evolves in a manner
consistent with previous measurements. The COSMOS/UltraVISTA Ks-selected
catalog covers a unique parameter space in both depth, area, and
multi-wavelength coverage and promises to be a useful tool for studying the
growth of the galaxy population out to z ~ 3 - 4.Comment: 20 pages, 14 figures. Accepted to the ApJSS. Catalog data products
available for download here:
http://www.strw.leidenuniv.nl/galaxyevolution/ULTRAVISTA
Stellar mass functions of galaxies at 4<z<7 from an IRAC-selected sample in COSMOS/UltraVISTA: limits on the abundance of very massive galaxies
We build a Spitzer IRAC complete catalog of objects, obtained by
complementing the -band selected UltraVISTA catalog with objects
detected in IRAC only. With the aim of identifying massive (i.e.,
) galaxies at , we consider the systematic effects
on the measured photometric redshifts from the introduction of an old and dusty
SED template and from the introduction of a bayesian prior taking into account
the brightness of the objects, as well as the systematic effects from different
star formation histories (SFHs) and from nebular emission lines in the recovery
of stellar population parameters. We show that our results are most affected by
the bayesian luminosity prior, while nebular emission lines and SFHs only
introduce a small dispersion in the measurements. Specifically, the number of
galaxies ranges from 52 to 382 depending on the adopted configuration.
Using these results we investigate, for the first time, the evolution of the
massive end of the stellar mass functions (SMFs) at . Given the rarity
of very massive galaxies in the early universe, major contributions to the
total error budget come from cosmic variance and poisson noise. The SMF
obtained without the introduction of the bayesian luminosity prior does not
show any evolution from to , implying that massive
galaxies could already be present when the Universe was ~Gyr old.
However, the introduction of the bayesian luminosity prior reduces the number
of galaxies with best fit masses by 83%, implying
a rapid growth of very massive galaxies in the first 1.5 Gyr of cosmic history.
From the stellar-mass complete sample, we identify one candidate of a very
massive (), quiescent galaxy at , with
MIPS m detection suggesting the presence of a powerful obscured AGN.Comment: 23 pages, 18 figures. ApJ accepte
The Progenitors of Local Ultra-massive Galaxies Across Cosmic Time: from Dusty Star-bursting to Quiescent Stellar Populations
Using the UltraVISTA catalogs, we investigate the evolution in the 11.4~Gyr
since of the progenitors of local ultra-massive galaxies (; UMGs), providing a complete and consistent
picture of how the most massive galaxies at have assembled. By selecting
the progenitors with a semi-empirical approach using abundance matching, we
infer a growth in stellar mass of 0.56 dex,
0.45~dex, and 0.27 dex from , ,
and , respectively, to . At , the progenitors of UMGs constitute
a homogeneous population of only quiescent galaxies with old stellar
populations. At , the contribution from star-forming galaxies
progressively increases, with the progenitors at being dominated by
massive (M), dusty (1--2.2 mag), star-forming (SFR100--400~M yr)
galaxies with a large range in stellar ages. At , 15\% of the
progenitors are quiescent, with properties typical of post-starburst galaxies
with little dust extinction and strong Balmer break, and showing a large
scatter in color. Our findings indicate that at least half of the stellar
content of local UMGs was assembled at , whereas the remaining was
assembled via merging from to the present. Most of the quenching of
the star-forming progenitors happened between and , in good
agreement with the typical formation redshift and scatter in age of UMGs
as derived from their fossil records. The progenitors of local UMGs, including
the star-forming ones, never lived on the blue cloud since . We propose an
alternative path for the formation of local UMGs that refines previously
proposed pictures and that is fully consistent with our findings.Comment: 20 pages, 15 figures (6 of which in appendix); accepted for
publication in the Astrophysical Journa
The Evolution of the Stellar Mass Functions of Star-Forming and Quiescent Galaxies to z = 4 from the COSMOS/UltraVISTA Survey
We present measurements of the stellar mass functions (SMFs) of star-forming
and quiescent galaxies to z = 4 using a sample of 95 675 galaxies in the
COSMOS/UltraVISTA field. Sources have been selected from the DR1 UltraVISTA
K_{s}-band imaging which covers a unique combination of a wide area (1.62
deg^2), to a significant depth (K_{s,tot} = 23.4). The SMFs of the combined
population are in good agreement with previous measurements and show that the
stellar mass density of the universe was only 50%, 10% and 1% of its current
value at z ~ 0.75, 2.0, and 3.5, respectively. The quiescent population drives
most of the overall growth, with the stellar mass density of these galaxies
increasing by 2.71^{+0.93}_{-0.22} dex since z = 3.5. At z > 2.5, star-forming
galaxies dominate the total SMF at all stellar masses, although a nonzero
population of quiescent galaxies persists to z = 4. Comparisons of the
K_{s}-selected star-forming galaxy SMFs to UV-selected SMFs at 2.5 < z < 4 show
reasonable agreement and suggests UV-selected samples are representative of the
majority of the stellar mass density at z > 3.5. We estimate the average mass
growth of individual galaxies by selecting galaxies at fixed cumulative number
density. The average galaxy with Log(M_{*}/M_{sun}) = 11.5 at z = 0.3 has grown
in mass by only 0.2 dex (0.3 dex) since z = 2.0(3.5), whereas those with
Log(M_{*}/M_{sun}) = 10.5 have grown by > 1.0 dex since z = 2. At z < 2, the
time derivatives of the mass growth are always larger for lower-mass galaxies,
which demonstrates that the mass growth in galaxies since that redshift is
mass-dependent and primarily bottom-up. Lastly, we examine potential sources of
systematic uncertainties on the SMFs and find that those from photo-z
templates, SPS modeling, and the definition of quiescent galaxies dominate the
total error budget in the SMFs.Comment: 18 pages paper, 12 pages appendix, 23 figures. Accepted for
publication in the Ap
In-depth analysis of defects in TiO2 compact electron transport layers and impact on performance and hysteresis of planar perovskite devices at low light
Properties of the electron transport layer (ETL) are known to influence the performance of lead halide perovskite solar cells (PSCs). But so far very little emphasis has been given on the increased impact of this layer at low light. In this work we compare the effect of thickness and coverage of a TiO2 compact layer on the performance and hysteresis of methyl ammonium lead iodide planar devices tested under 200 lux vs. 1 sun illumination. Standard TiO2 layers are produced with incremental thickness and coverage using sequential spray pyrolysis of a Ti-acetylacetonate precursor (0–50 sprays, 1 spray ~ 1 nm TiO2). Thorough materials characterisation combining FEG-SEM, XPS, and cyclic voltammetry shows that a crystalline, nearly pin-hole free TiO2 layer is achieved by deposition of ≥15 sprays over small to large areas (0.2 mm2–1 cm2). Device performance is affected by two main parameters, namely the coverage yield and thickness of the TiO2 layer, especially under 200 lux illumination. A 25 vs. 50 sprays-TiO2 layer is found to provide the best compromise between coverage and thickness and avoid charge recombination at the TiO2/perovskite interface whilst minimizing resistive losses with 11.7% average PCE at 200 lux vs 7.8% under 1 sun. Finally, the analysis of I/V forward vs. reverse scans and open circuit voltage decay data suggests that hysteresis is greatly affected by the capacitive properties of the ETL at low light, whilst other phenomena such as ion migrations may dominate under 1 sun
Combined analysis of the integrated Sachs-Wolfe effect and cosmological implications
We present a global measurement of the integrated Sachs-Wolfe (ISW) effect
obtained by cross-correlating all relevant large scale galaxy data sets with
the cosmic microwave background radiation map provided by the Wilkinson
Microwave Anisotropy Probe. With these measurements, the overall ISW signal is
detected at the ~ 4.5 sigma level. We also examine the cosmological
implications of these measurements, particularly the dark energy equation of
state w, its sound speed, and the overall curvature of the Universe. The flat
LCDM model is a good fit to the data and, assuming this model, we find that the
ISW data constrain Omega_m = 0.20 +0.19 -0.11 at the 95% confidence level. When
we combine our ISW results with the latest baryon oscillation and supernovae
measurements, we find that the result is still consistent with a flat LCDM
model with w = -1 out to redshifts z > 1.Comment: 24 pages, 15 figures. Version accepted by PRD. Improved quasar data,
revised parameter constraint
How to Measure Galaxy Star Formation Histories. I. Parametric Models
Parametric models for galaxy star-formation histories (SFHs) are widely used,
though they are known to impose strong priors on physical parameters. This has
consequences for measurements of the galaxy stellar-mass function (GSMF),
star-formation-rate density (SFRD) and star-forming main sequence (SFMS). We
investigate the effects of the exponentially declining, delayed exponentially
declining, lognormal and double power law SFH models using BAGPIPES. We
demonstrate that each of these models imposes strong priors on specific
star-formation rates (sSFRs), potentially biasing the SFMS, and also imposes a
strong prior preference for young stellar populations. We show that stellar
mass, SFR and mass-weighted age inferences from high-quality mock photometry
vary with the choice of SFH model by at least 0.1, 0.3 and 0.2 dex
respectively. However the biases with respect to the true values depend more on
the true SFH shape than the choice of model. We also demonstrate that
photometric data cannot discriminate between SFH models, meaning it is
important to perform independent tests to find well-motivated priors. We
finally fit a low-redshift, volume-complete sample of galaxies from the Galaxy
and Mass Assembly (GAMA) Survey with each model. We demonstrate that our
stellar masses and SFRs at redshift, are consistent with other
analyses. However, our inferred cosmic SFRDs peak at , approximately
6 Gyr later than direct observations suggest, meaning our mass-weighted ages
are significantly underestimated. This makes the use of parametric SFH models
for understanding mass assembly in galaxies challenging. In a companion paper
we consider non-parametric SFH models.Comment: 20 pages, 12 figures, ApJ accepte
A massive quiescent galaxy at redshift 4.658
A. C. Carnall thanks the Leverhulme Trust for their support via a Leverhulme Early Career Fellowship. R. J. McLure, J. S. Dunlop, D. J. McLeod, V. Wild, R. Begley, C. T. Donnan and M. L. Hamadouche acknowledge the support of the Science and Technology Facilities Council. F. Cullen acknowledges support from a UKRI Frontier Research Guarantee Grant (grant reference EP/X021025/1). A. Cimatti acknowledges support from the grant PRIN MIUR 2017 - 20173ML3WW 001.The extremely rapid assembly of the earliest galaxies during the first billion years of cosmic history is a major challenge for our understanding of galaxy formation physics (1; 2; 3; 4; 5). The advent of JWST has exacerbated this issue by confirming the existence of galaxies in significant numbers as early as the first few hundred million years (6; 7; 8). Perhaps even more surprisingly, in some galaxies, this initial highly efficient star formation rapidly shuts down, or quenches, giving rise to massive quiescent galaxies as little as 1.5 billion years after the Big Bang (9; 10), however, due to their faintness and red colour, it has proven extremely challenging to learn about these extreme quiescent galaxies, or to confirm whether any exist at earlier times. Here we report the spectroscopic confirmation of a massive quiescent galaxy, GS-9209, at redshift, z = 4.658, just 1.25 billion years after the Big Bang, using JWST NIRSpec. From these data we infer a stellar mass of M∗ = 3.8 ± 0.2 × 1010 M⊙, which formed over a ≃ 200 Myr period before this galaxy quenched its star formation activity at z=6.5+0.2−0.5, when the Universe was ≃ 800 million years old. This galaxy is both a likely descendent of the highest-redshift submillimetre galaxies and quasars, and a likely progenitor for the dense, ancient cores of the most massive local galaxies.PostprintPeer reviewe
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