37,621 research outputs found
Transthyretin familial amyloid polyneuropathy impact on health-related quality of life
info:eu-repo/semantics/publishedVersio
Contributions from Dilatonic Strings to the Flat Behaviour of the Rotational Curves in Galaxies
We analyse the flat behaviour of the rotational curves in some galaxies in
the framework of a dilatonic, current-carrying string. We determine the
expression of the tangential velocity of test objects following a stable
circular equatorial orbit in this spacetime.Comment: This version to be published in the Int. Journal of Modern Phys.
Qualidade sanitĂĄria de sementes de nĂł-de-cachorro (Heteropterys tomentosa).
bitstream/item/82283/1/CT104.pd
The Power Spectrum of Galaxies in the Nearby Universe
We compute the power spectrum of galaxy density fluctuations in a recently
completed redshift survey of optically-selected galaxies in the southern
hemisphere (SSRS2). The amplitude and shape of the SSRS2 power spectrum are
consistent with results of the Center for Astrophysics redshift survey of the
northern hemisphere (CfA2), including the abrupt change of slope on a scale of
30-50Mpc/h; these results are reproducible for independent volumes of space and
variations are consistent with the errors estimated from mock surveys. Taken
together, the SSRS2 and CfA2 form a complete sample of 14,383 galaxies which
covers one-third of the sky. The power spectrum of this larger sample continues
to rise on scales up to ~ 200Mpc/h, with weak evidence for flattening on the
largest scales. The SSRS2+CfA2 power spectrum and the power spectrum
constraints implied by COBE are well-matched by an Omega*h ~ 0.2,
Omega+lambda_0=1 CDM model with minimal biasing of optically-selected galaxies.Comment: Accepted for publication in The Astrophysical Journal Letters, Sept.
23, 1994. 10 pages uuencoded compressed postscript, including two figures.
JHU-9410200
PAIRWISE VELOCITIES OF GALAXIES IN THE CFA AND SSRS2 REDSHIFT SURVEYS
(compressed version) We combine the CfA Redshift Survey (CfA2) and the
Southern Sky Redshift Survey (SSRS2) to estimate the pairwise velocity
dispersion of galaxies \sig12 on a scale of \sim 1 \hmpc. Both surveys are
complete to an apparent magnitude limit . Our sample includes 12,812
galaxies distributed in a volume 1.8 \times 10^6 \hmpc3. We conclude: 1) The
pairwise velocity dispersion of galaxies in the combined CfA2+SSRS2 redshift
survey is \sig12=540 \kms \pm 180 \kms. Both the estimate and the variance of
\sig12 significantly exceed the canonical values \sig12=340 \pm40 measured
by Davis \& Peebles (1983) using CfA1. 2) We derive the uncertainty in \sig12
from the variation among subsamples with volumes on the order of \hmpc3. This variation is nearly an order of magnitude larger than the
formal error, 36 \kms, derived using least-squares fits to the CfA2+SSRS2
correlation function. This variation among samples is consistent with the
conclusions of Mo \etal (1993) for a number of smaller surveys and with the
analysis of CfA1 by Zurek \etal (1994). 3) When we remove Abell clusters with
from our sample, the pairwise velocity dispersion of the remaining
galaxies drops to 295 \pm 99 \kms. Thus the dominant source of variance in
\sig12 is the shot noise contributed by dense virialized systems. 4) The
distribution of pairwise velocities is consistent with an isotropic exponential
with velocity dispersion independent of scale.Comment: 61 pages uuencoded, compressed postscript in 5 pieces. Also available
in one piece at http://www.dao.nrc.ca/DAO/SCIENCE/science.htm
Removing point sources from CMB maps
For high-precision cosmic microwave background (CMB) experiments,
contamination from extragalactic point sources is a major concern. It is
therefore useful to be able to detect and discard point source contaminated
pixels using the map itself. We show that the sensitivity with which this can
be done can often be greatly improved (by factors between 2.5 and 18 for the
upcoming Planck mission) by a customized hi-pass filtering that suppresses
fluctuations due to CMB and diffuse galactic foregrounds. This means that point
source contamination will not severely degrade the cleanest Planck channels
unless current source count estimates are off by more than an order of
magnitude. A catalog of around 40,000 far infra-red sources at 857 GHz may be a
useful by-product of Planck.Comment: 4 pages, with 2 figures included. Minor revisions to match accepted
version. Color figure and links at http://www.sns.ias.edu/~max/cleaning.html
(faster from the US), from http://www.mpa-garching.mpg.de/~max/cleaning.html
(faster from Europe) or from [email protected], and Angelica's foreground links at
http://www.sns.ias.edu/~angelica/foreground.htm
Redshift-Distance Survey of Early-Type Galaxies. IV. Dipoles of the Velocity Field
We use the recently completed redshift-distance survey of nearby early-type
galaxies (ENEAR) to measure the dipole component of the peculiar velocity field
to a depth of cz ~ 6000 km/s. The sample consists of 1145 galaxies brighter
than m_B=14.5 and cz < 7000 km/s, uniformly distributed over the whole sky, and
129 fainter cluster galaxies within the same volume. Most of the Dn-sigma
distances were obtained from new spectroscopic and photometric observations
conducted by this project, ensuring the homogeneity of the data over the whole
sky. These 1274 galaxies are objectively assigned to 696 objects -- 282
groups/clusters and 414 isolated galaxies. We find that within a volume of
radius ~ 6000 km/s, the best-fitting bulk flow has an amplitude of |vbulk| =220
+/- 42 km/s in the CMB restframe, pointing towards l=304 +/- 16 degrees, b=25
+/- 11 degrees. The error in the amplitude includes statistical, sampling and
possible systematic errors. This solution is in excellent agreement with that
obtained by the SFI Tully-Fisher survey. Our results suggest that most of the
motion of the Local Group is due to fluctuations within 6000 km/s, in contrast
to recent claims of large amplitude bulk motions on larger scales.Comment: 11 pages, 2 figures, ApJL, accepted (updated results; matches
accepted version
Retired galaxies: not to be forgotten in the quest of the star formation -- AGN connection
We propose a fresh look at the Main Galaxy Sample of the Sloan Digital Sky
Survey by packing the galaxies in stellar mass and redshift bins. We show how
important it is to consider the emission-line equivalent widths, in addition to
the commonly used emission-line ratios, to properly identify retired galaxies
(i.e. galaxies that have stopped forming stars and are ionized by their old
stellar populations) and not mistake them for galaxies with low-level nuclear
activity. We find that the proportion of star-forming galaxies decreases with
decreasing redshift in each mass bin, while that of retired galaxies increases.
Galaxies with have formed all their stars at
redshift larger than 0.4. The population of AGN hosts is never dominant for
galaxy masses larger than . We warn about the effects of
stacking galaxy spectra to discuss galaxy properties. We estimate the lifetimes
of active galactic nuclei (AGN) relying entirely on demographic arguments ---
i.e. without any assumption on the AGN radiative properties. We find
upper-limit lifetimes of about 1--5 Gyr for detectable AGN in galaxies with
masses between --. The lifetimes of the AGN-dominated
phases are a few yr. Finally, we compare the star-formation histories of
star-forming, AGN and retired galaxies as obtained by the spectral synthesis
code STARLIGHT. Once the AGN is turned on it inhibits star formation for the
next 0.1 Gyr in galaxies with masses around , 1
Gyr in galaxies with masses around .Comment: accepted for MNRAS figure resolution has been degraded with respect
to what will be published in MNRA
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