114 research outputs found
How does the grouping scheme affect the Wiener Filter reconstruction of the local Universe?
High quality reconstructions of the three dimensional velocity and density
fields of the local Universe are essential to study the local Large Scale
Structure. In this paper, the Wiener Filter reconstruction technique is applied
to galaxy radial peculiar velocity catalogs to understand how the Hubble
constant (H0) value and the grouping scheme affect the reconstructions. While
H0 is used to derive radial peculiar velocities from galaxy distance
measurements and total velocities, the grouping scheme serves the purpose of
removing non linear motions. Two different grouping schemes (based on the
literature and a systematic algorithm) as well as five H0 values ranging from
72 to 76 km/s/Mpc are selected. The Wiener Filter is applied to the resulting
catalogs. Whatever grouping scheme is used, the larger H0 is, the larger the
infall onto the local Volume is. However, this conclusion has to be strongly
mitigated: a bias minimization scheme applied to the catalogs after grouping
suppresses this effect. At fixed H0, reconstructions obtained with catalogs
grouped with the different schemes exhibit structures at the proper location in
both cases but the latter are more contrasted in the less aggressive scheme
case: having more constraints permits an infall from both sides onto the
structures to reinforce their overdensity. Such findings highlight the
importance of a balance between grouping to suppress non linear motions and
preserving constraints to produce an infall onto structures expected to be
large overdensities. Such an observation is promising to perform constrained
simulations of the local Universe including its massive clusters.Comment: Accepted for publication in MNRAS, 10 pages, 6 figures, 3 table
The Mid-Infrared Tully-Fisher Relation: Calibration of the SNIa Scale and Ho
This paper builds on a calibration of the SNIa absolute distance scale begun
with a core of distances based on the correlation between galaxy rotation rates
and optical Ic band photometry. This new work extends the calibration through
the use of mid-infrared photometry acquired at 3.6 microns with Spitzer Space
Telescope. The great virtue of the satellite observations is constancy of the
photometry at a level better than 1% across the sky. The new calibration is
based on 39 individual galaxies and 8 clusters that have been the sites of well
observed SNIa. The new 3.6 micron calibration is not yet as extensively based
as the Ic band calibration but is already sufficient to justify a preliminary
report. Distances based on the mid-infrared photometry are 2% greater in the
mean than reported at Ic band. This difference is only marginally significant.
The Ic band result is confirmed with only a small adjustment. Incorporating a
1% decrease in the LMC distance, the present study indicates Ho = 75.2 +/- 3.0
km/s/Mpc.Comment: Accepted for publication in The Astrophysical Journal Letters, 6
pages, 2 figure
Bimodality of Galaxy Disk Central Surface Brightness Distribution in the Spitzer 3.6 micron band
We report on measurements of the disk central surface brightnesses (mu0) at
3.6 microns for 438 galaxies selected by distance and absolute magnitude
cutoffs from the 2350+ galaxies in the Spitzer Survey of Stellar Structure in
Galaxies (S4G), one of the largest and deepest homogeneous mid-infrared
datasets of nearby galaxies. Our sample contains nearly 3 times more galaxies
than the most recent study of the mu0 distribution. We demonstrate that there
is a bimodality in the distribution of mu0. Between the low and high surface
brightness galaxy regimes there is a lack of intermediate surface brightness
galaxies.
Caveats invoked in the literature from small number statistics to the
knowledge of the environmental influences, and possible biases from low signal
to noise data or corrections for galaxy inclination are investigated. Analyses
show that the bimodal distribution of mu0 cannot be due to any of these biases
or statistical fluctuations. It is highly probable that galaxies settle in two
stable modes: a dark matter dominated mode where the dark matter dominates at
all radii - this gives birth to low surface brightness galaxies - and a
baryonic matter dominated mode where the baryons dominate the dark matter in
the central parts - this gives rise to the high surface brightness disks. The
lack of intermediate surface brightness objects suggests that galaxies avoid
(staying in) a mode where dark matter and baryons are co-dominant in the
central parts of galaxies.Comment: Accepted for publication in MNRAS, 9 pages, 10 figures, 1 tabl
Euclid legacy science prospects
With the immense number of images, data, and sources that Euclid will
deliver, the consortium will be in a unique position to
create/provide/construct legacy catalogues. The latter will have exquisite
imaging quality and good near-infrared spectroscopy, with impact on many areas
of galaxy science. These proceedings review the prospects and scientific output
that Euclid will be able to achieve in areas of galaxy and active galactic
nucleus (AGN) evolution, the local and primeval Universe, studies of the Milky
Way and stellar populations, supernovae (SN) and transients, Solar System
objects, exoplanets, strong lensing and galaxy clusters.Comment: 6 pages, contribution to the ICHEP2022 conference proceedings
accompanying the ''Euclid in a nutshell'' and ''Euclid: performance on main
cosmological parameter science'' contribution
Statistically bias-minimized peculiar velocity catalogs from Gibbs point processes and Bayesian inference
Galaxy peculiar velocities are excellent cosmological probes provided that
biases inherent to their measurements are contained before any study. This
paper proposes a new algorithm based on an object point process model whose
probability density is built to statistically reduce the effects of Malmquist
biases and uncertainties due to lognormal errors in radial peculiar velocity
catalogs. More precisely, a simulated annealing algorithm permits maximizing
the probability density describing the point process model. The resulting
configurations are bias-minimized catalogs. Tests are conducted on synthetic
catalogs mimicking the second and third distance modulus catalogs of the
Cosmicflows project from which peculiar velocity catalogs are derived. By
reducing the local peculiar velocity variance in catalogs by an order of
magnitude, the algorithm permits recovering the expected one while preserving
the small-scale velocity correlation. It also permits retrieving the expected
clustering. The algorithm is then applied to the observational catalogs. The
large-scale structure reconstructed with the Wiener-filter technique applied to
the bias-minimized observational catalogs matches with great success the local
cosmic web as depicted by redshift surveys of local galaxies. These new
bias-minimized versions of peculiar velocity catalogs can be used as a starting
point for several studies from possibly estimating the most probable Hubble
constant, H0, value to the production of simulations constrained to reproduce
the local Universe.Comment: Accepted for publication in A&A, 26 pages, 22 figures, 3 table
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