37 research outputs found
Joint analysis of the thermal Sunyaev-Zeldovich effect and 2MASS galaxies: Probing gas physics in the local Universe and beyond
We present a first joint analysis of the power spectra of the thermal
Sunyaev-Zeldovich (tSZ) effect measured by the Planck and the number density
fluctuations of galaxies in the 2MASS redshift survey (2MRS) catalog, including
their cross-correlation. Combining these measurements with the cosmic microwave
background (CMB) data and CMB lensing of Planck assuming a flat CDM
model, we constrain the mass bias parameter as
[, where ], i.e., the Planck
cluster mass should be lower than the true mass. The mass bias
determined by the 2MRS-tSZ cross-power spectrum alone is consistent with that
determined by the tSZ auto-power spectrum alone, suggesting that this large
mass bias is not due to obvious systematics in the tSZ data. We find that the
2MRS-tSZ cross-power spectrum is more sensitive to less massive halos than the
tSZ auto-power spectrum and it significantly improves a constraint on the mass
dependence of the mass bias. The redshift dependence is not strongly
constrained since the multipole range in which high redshift clusters mainly
contribute to the tSZ auto is dominated by the contaminating sources. We
conclude that no strong mass or redshift evolution of the mass bias is needed
to explain the data.Comment: 14 pages, 11 figures, MNRAS accepted, references correcte
Ray-tracing log-normal simulation for weak gravitational lensing: application to the cross-correlation with galaxies
We present an algorithm to self-consistently generate mock weak gravitational
lensing convergence fields and galaxy distributions in redshift space. We
generate three-dimensional cosmic density fields that follow a log-normal
distribution, and ray-trace them to produce convergence maps. As we generate
the galaxy distribution from the same density fields in a manner consistent
with ray-tracing, the galaxy-convergence cross-power spectrum measured from the
mock agrees with the theoretical expectation with high precision. We use this
simulation to forecast the quality of galaxy-shear cross-correlation
measurements from the Subaru Hyper Suprime-Cam (HSC) and Prime Focus
Spectrograph (PFS) surveys. We find that the nominal HSC and PFS surveys would
detect the cross power spectra with signal-to-noise ratios of 20 and 5 at the
lowest () and highest () redshift bins, respectively.Comment: 22 pages, 10 figures, accepted to JCAP. The simulation code is
available at https://wwwmpa.mpa-garching.mpg.de/~komatsu/codes.htm
Suzaku Observation of Abell 1555 and Abell 1558: Searching for Non-thermal Emission from Large Scale Structure Formation
We report X-ray observations of two galaxy clusters Abell 1555 and Abell 1558
with Suzaku, which are included in a large scale filamentary structure and a
supercluster, to search for non-thermal emission driven by shocks produced in
structure formation. These two clusters are detected by Suzaku/XIS for the
first time in the X-ray band of 0.5-7 keV. No significant flux is detected by
HXD in the energy band of 13-40 keV, and upper limits are reported. From the
analysis of the XIS data, we find that the spectrum of A1555 is fit by a
thermal plus power-law model, significantly better than a single-temperature
pure thermal spectrum. If this power-law component is due to inverse-Compton
scattering, the fraction of total baryon energy imparted to non-thermal
electrons is consistent with the typical value inferred from the observation of
other clusters. However, other scenarios (e.g., under lying AGNs,
multi-temperature thermal models) cannot be excluded and further investigation
of this system is desired. Basic physical properties of A1555 (e.g., total
mass) are also reported.Comment: 10 pages, 6 figures. Accepted for publication in the PAS
Generating Log-normal Mock Catalog of Galaxies in Redshift Space
We present a public code to generate a mock galaxy catalog in redshift space
assuming a log-normal probability density function (PDF) of galaxy and matter
density fields. We draw galaxies by Poisson-sampling the log-normal field, and
calculate the velocity field from the linearised continuity equation of matter
fields, assuming zero vorticity. This procedure yields a PDF of the pairwise
velocity fields that is qualitatively similar to that of N-body simulations. We
check fidelity of the catalog, showing that the measured two-point correlation
function and power spectrum in real space agree with the input precisely. We
find that a linear bias relation in the power spectrum does not guarantee a
linear bias relation in the density contrasts, leading to a cross-correlation
coefficient of matter and galaxies deviating from unity on small scales. We
also find that linearising the Jacobian of the real-to-redshift space mapping
provides a poor model for the two-point statistics in redshift space. That is,
non-linear redshift-space distortion is dominated by non-linearity in the
Jacobian. The power spectrum in redshift space shows a damping on small scales
that is qualitatively similar to that of the well-known Fingers-of-God (FoG)
effect due to random velocities, except that the log-normal mock does not
include random velocities. This damping is a consequence of non-linearity in
the Jacobian, and thus attributing the damping of the power spectrum solely to
FoG, as commonly done in the literature, is misleading.Comment: 38 pages, 16 figures, code publicly available as "lognormal_galaxies"
at http://wwwmpa.mpa-garching.mpg.de/~komatsu/codes.html Matches published
version : added figures and explanatory comment
Infrared Spectral Energy Distribution of Galaxies in the AKARI All Sky Survey: Correlations with Galaxy Properties, and Their Physical Origin
We have studied the properties of more than 1600 low-redshift galaxies by
utilizing high-quality infrared flux measurements of the AKARI All-Sky Survey
and physical quantities based on optical and 21-cm observations. Our goal is to
understand the physics determining the infrared spectral energy distribution
(SED). The ratio of the total infrared luminosity L_TIR, to the star-formation
rate (SFR) is tightly correlated by a power-law to specific SFR (SSFR), and
L_TIR is a good SFR indicator only for galaxies with the largest SSFR. We
discovered a tight linear correlation for normal galaxies between the radiation
field strength of dust heating, estimated by infrared SED fits (U_h), and that
of galactic-scale infrared emission (U_TIR ~ L_TIR/R^2), where R is the optical
size of a galaxy. The dispersion of U_h along this relation is 0.3 dex,
corresponding to 13% dispersion in the dust temperature. This scaling and the
U_h/U_TIR ratio can be explained physically by a thin layer of heating sources
embedded in a thicker, optically-thick dust screen. The data also indicate that
the heated fraction of the total dust mass is anti-correlated to the dust
column density, supporting this interpretation. In the large U_TIR limit, the
data of circumnuclear starbursts indicate the existence of an upper limit on
U_h, corresponding to the maximum SFR per gas mass of ~ 10 Gyr^{-1}. We find
that the number of galaxies sharply drops when they become optically thin
against dust-heating radiation, suggesting that a feedback process to galaxy
formation (likely by the photoelectric heating) is working when dust-heating
radiation is not self-shielded on a galactic scale. Implications are discussed
for the M_HI-size relation, the Kennicutt-Schmidt relation, and galaxy
formation in the cosmological context.Comment: 29 pages including 28 figures. matches the published version (PASJ
2011 Dec. 25 issue). The E-open option was chosen for this article, i.e., the
official version available from PASJ site
(http://pasj.asj.or.jp/v63/n6/630613/630613-frame.html) without restrictio
The thermal and gravitational energy densities in the large-scale structure of the Universe
As cosmic structures form, matter density fluctuations collapse
gravitationally and baryonic matter is shock-heated and thermalized. We
therefore expect a connection between the mean gravitational potential energy
density of collapsed halos, , and the mean thermal
energy density of baryons, . These quantities can be obtained
using two fundamentally different estimates: we compute
using the theoretical framework of the halo model which is driven by dark
matter statistics, and measure using the Sunyaev-Zeldovich
(SZ) effect which probes the mean thermal pressure of baryons. First, we derive
that, at the present time, about 90% of originates from
massive halos with . Then, using our measurements of the SZ
background, we find that accounts for about 80% of the
kinetic energy of the baryons available for pressure in halos at . This constrains the amount of non-thermal pressure, e.g., due to bulk and
turbulent gas motion sourced by mass accretion, to be about at .Comment: 11 pages + references, 4 figures, 2 tables. (v2) Expanded discussion
on the modelling uncertainty. (v3) Fixed a minor typo in Eq.(22). Accepted
for publication in the Astrophysical Journal. Julia codes to reproduce the
figures and tables are available in
https://github.com/komatsu5147/OmegaGrav.j