920 research outputs found
Absolute properties of BG Ind - a bright F3 system just leaving the Main Sequence
We present photometric and spectroscopic analysis of the bright detached
eclipsing binary BG Ind. The masses of the components are found to be 1.428 +-
0.008 and 1.293 +- 0.008 Msun and the radii to be 2.290+-0.017 and 1.680+-0.038
Rsun for primary and secondary stars, respectively. Spectra- and
isochrone-fitting coupled with color indices calibration yield
[Fe/H]=-0.2+-0.1. At an age of 2.65+-0.20 Gyr BG Ind is well advanced in the
main-sequence evolutionary phase - in fact, its primary is at TAMS or just
beyond it. Together with three similar systems (BK Peg, BW Aqr and GX Gem) it
offers an interesting opportunity to test the theoretical description of
overshooting in the critical mass range 1.2-1.5 Msun.Comment: 8 pages, 5 figures, corrected bugs in author lis
Influence of star-forming galaxy selection on the galaxy main sequence
This work aims to determine how the galaxy main sequence (MS) changes using
seven different commonly used methods to select the star-forming galaxies
within VIPERS data over . The form and redshift evolution of
the MS will then be compared between selection methods. The star-forming
galaxies were selected using widely known methods: a specific star-formation
rate (sSFR), Baldwin, Phillips and Terlevich (BPT) diagram, 4000\AA\ spectral
break (D4000) cut and four colour-colour cuts: NUVrJ, NUVrK, u-r, and UVJ. The
main sequences were then fitted for each of the seven selection methods using a
Markov chain Monte Carlo forward modelling routine, fitting both a linear main
sequence and a MS with a high-mass turn-over to the star-forming galaxies. This
was done in four redshift bins of , ,
, and . The slopes of all star-forming
samples were found to either remain constant or increase with redshift, and the
scatters were approximately constant. There is no clear redshift dependency of
the presence of a high-mass turn-over for the majority of samples, with the
NUVrJ and NUVrK being the only samples with turn-overs only at low redshift. No
samples have turn-overs at all redshifts. Star-forming galaxies selected with
sSFR and u-r are the only samples to have no high-mass turn-over in all
redshift bins. The normalisation of the MS increases with redshift, as
expected. The scatter around the MS is lower than the 0.3~dex
typically seen in MS studies for all seven samples. The lack, or presence, of a
high-mass turn-over is at least partially a result of the method used to select
star-forming galaxies. However, whether a turn-over should be present or not is
unclear.Comment: 20 pages, 3 appendices, 14 figures, 5 tables, accepted for
publication in Astronomy & Astrophysic
Variation of optical and infrared properties of galaxies with their surface brightness
Although low surface brightness galaxies (LSBs) contribute a large fraction
to the number density of galaxies, their properties are still poorly known.
LSBs are often considered dust poor, based only on a few studies. We use, for
the first time, a large sample of LSBs and high surface brightness galaxies
(HSBs) with deep observational data to study their dust properties as a
function of surface brightness. Our sample consists of 1631 optically selected
galaxies at from the North Ecliptic Pole (NEP) wide field. We use the
large set of data available in this field, from UV to FIR. We measured the
optical size and the surface brightness of the targets, and analyzed their
spectral energy distribution using the CIGALE fitting code. We found that the
specific star formation rate and specific infrared luminosity (total infrared
luminosity per stellar mass) remain mostly flat as a function of surface
brightness for both LSBs and HSBs that are star-forming but decline steeply for
the quiescent galaxies. The majority of LSBs in our sample have negligible dust
attenuation (A mag), except for about 4% of them that show
significant attenuation with a mean A of 0.8 mag. We found that these
LSBs also have a high -band mass-to-light ratio (
M/L), and show similarity to the extreme giant LSBs from
the literature, indicating a possibly higher dust attenuation in giant LSBs as
well. This work provides a large catalog of LSBs and HSBs with detailed
measurements of their several optical and infrared physical properties. Our
results suggest that the dust content of LSBs is more varied than previously
thought, with some of them having significant attenuation making them fainter
than their intrinsic value. This will have serious implications for the
observation and analysis of LSBs with current/upcoming surveys like JWST and
LSST.Comment: 16 pages, 12 figures, accepted for publication in A&
The VIMOS Public Extragalactic Redshift Survey (VIPERS): On the correct recovery of the count-in-cell probability distribution function
We compare three methods to measure the count-in-cell probability density
function of galaxies in a spectroscopic redshift survey. From this comparison
we found that when the sampling is low (the average number of object per cell
is around unity) it is necessary to use a parametric method to model the galaxy
distribution. We used a set of mock catalogues of VIPERS, in order to verify if
we were able to reconstruct the cell-count probability distribution once the
observational strategy is applied. We find that in the simulated catalogues,
the probability distribution of galaxies is better represented by a Gamma
expansion than a Skewed Log-Normal. Finally, we correct the cell-count
probability distribution function from the angular selection effect of the
VIMOS instrument and study the redshift and absolute magnitude dependency of
the underlying galaxy density function in VIPERS from redshift to .
We found very weak evolution of the probability density distribution function
and that it is well approximated, independently from the chosen tracers, by a
Gamma distribution.Comment: 14 pages, 11 figures, 2 table
The VIMOS Public Extragalactic Redshift Survey (VIPERS): A quiescent formation of massive red-sequence galaxies over the past 9 Gyr
We explore the evolution of the Colour-Magnitude Relation (CMR) and
Luminosity Function (LF) at 0.4<z<1.3 from the VIMOS Public Extragalactic
Redshift Survey (VIPERS) using ~45,000 galaxies with precise spectroscopic
redshifts down to i'_AB<22.5 over ~10.32 deg^2 in two fields. From z=0.5 to
z=1.3 the LF and CMR are well defined for different galaxy populations and
M^*_B evolves by ~1.04(1.09)+/-0.06(0.10) mag for the total (red) galaxy
sample. We compare different criteria for selecting early-type galaxies (ETGs):
(1) fixed cut in rest-frame (U-V) colours, (2) evolving cut in (U-V) colours,
(3) rest-frame (NUV-r')-(r'-K) colour selection, and (4) SED classification.
Regardless of the method we measure a consistent evolution of the red-sequence
(RS). Between 0.4<z<1.3 we find a moderate evolution of the RS intercept of
Delta(U-V)=0.28+/-0.14 mag, favouring exponentially declining star formation
(SF) histories with SF truncation at 1.7<=z<=2.3. Together with the rise in the
ETG number density by 0.64 dex since z=1, this suggests a rapid build-up of
massive galaxies (M>10^11 M_sun) and expeditious RS formation over a short
period of ~1.5 Gyr starting before z=1. This is supported by the detection of
ongoing SF in ETGs at 0.9<z<1.0, in contrast with the quiescent red stellar
populations of ETGs at 0.5<z<0.6. There is an increase in the observed CMR
scatter with redshift, two times larger than in galaxy clusters and at variance
with theoretical models. We discuss possible physical mechanisms that support
the observed evolution of the red galaxy population. Our findings point out
that massive galaxies have experienced a sharp SF quenching at z~1 with only
limited additional merging. In contrast, less-massive galaxies experience a mix
of SF truncation and minor mergers which build-up the low- and
intermediate-mass end of the CMR.Comment: 27 pages, 21 figures, accepted for publication in A&
A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).XIII. The role of ram-pressure stripping in transforming the diffuse and ultra-diffuse galaxies in the Virgo cluster
Low-surface-brightness galaxies (LSBs) contribute to a significant fraction
of all the galaxies in the Universe. Ultra-diffuse galaxies (UDGs) form a
subclass of LSBs that has attracted a lot of attention in recent years
(although its definition may vary between studies). Although UDGs are found in
large numbers in galaxy clusters, groups, and in the field, their formation and
evolution are still very much debated. Using a comprehensive set of
multiwavelength data from the NGVS (optical), VESTIGE (H narrowband),
and GUViCS (UV) surveys, we studied a sample of 64 diffuse galaxies and UDGs in
the Virgo cluster to investigate their formation history. We analyzed the
photometric colors and surface-brightness profiles of these galaxies and then
compared them to models of galaxy evolution, including ram-pressure stripping
(RPS) events to infer any possible strong interactions with the hot cluster gas
in the past. While our sample consists mainly of red LSBs, which is typical in
cluster environments, we found evidence of a color variation with the
cluster-centric distance. Blue, HI-bearing, star-forming diffuse galaxies are
found at larger distances from the cluster center than the rest of the sample.
The comparison of our models with multifrequency observations suggests that
most of the galaxies of the sample might have undergone a strong RPS event in
their lifetime, on average 1.6 Gyr ago (with a large dispersion, and RPS still
ongoing for some of them). This process resulted in the transformation of
initially gas-rich diffuse blue galaxies into gas-poor and red ones that form
the dominant population now, the more extreme UDGs having undergone the process
in a more distant past on average. The RPS in dense environments could be one
of the major mechanisms for the formation of the large number of quiescent UDGs
we observe in galaxy clusters.Comment: 57 pages, 14 Figures, accepted for publication in A&
The VIMOS Public Extragalactic Redshift Survey - Searching for Cosmic Voids
The characterisation of cosmic voids gives unique information about the
large-scale distribution of galaxies, their evolution and the cosmological
model. We identify and characterise cosmic voids in the VIMOS Public
Extragalactic Redshift Survey (VIPERS) at redshift 0.55 < z < 0.9. A new void
search method is developed based upon the identification of empty spheres that
fit between galaxies. The method can be used to characterise the cosmic voids
despite the presence of complex survey boundaries and internal gaps. We
investigate the impact of systematic observational effects and validate the
method against mock catalogues. We measure the void size distribution and the
void-galaxy correlation function. We construct a catalogue of voids in VIPERS.
The distribution of voids is found to agree well with the distribution of voids
found in mock catalogues. The void-galaxy correlation function shows
indications of outflow velocity from the voids
S2COSMOS: evolution of gas mass with redshift using dust emission
We investigate the evolution of the gas mass fraction for galaxies in the COSMOS field using submillimetre emission from dust at 850μm. We use stacking methodologies on the 850 μm S2COSMOS map to derive the gas mass fraction of galaxies out to high redshifts, 0 ≤ z ≤ 5, for galaxies with stellar masses of 109.
North Ecliptic Pole merging galaxy catalogue
Aims. We aim to generate a catalogue of merging galaxies within the 5.4 sq. deg. North Ecliptic Pole over the redshift range 0.0 \u3c z \u3c 0.3. To do this, imaging data from the Hyper Suprime-Cam are used along with morphological parameters derived from these same data.
Methods. The catalogue was generated using a hybrid approach. Two neural networks were trained to perform binary merger non-merger classifications: one for galaxies with z \u3c 0.15 and another for 0.15 ≤ z \u3c 0.30. Each network used the image and morphological parameters of a galaxy as input. The galaxies that were identified as merger candidates by the network were then visually checked by experts. The resulting mergers will be used to calculate the merger fraction as a function of redshift and compared with literature results.
Results. We found that 86.3% of galaxy mergers at z \u3c 0.15 and 79.0% of mergers at 0.15 ≤ z \u3c 0.30 are expected to be correctly identified by the networks. Of the 34 264 galaxies classified by the neural networks, 10 195 were found to be merger candidates. Of these, 2109 were visually identified to be merging galaxies. We find that the merger fraction increases with redshift, consistent with literature results from observations and simulations, and that there is a mild star-formation rate enhancement in the merger population of a factor of 1.102 ± 0.084
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