22 research outputs found
SPECTRA OF YOUNG GALAXIES
Invited review, Ringberg conference on "Galaxies in the Young Universe"
(Sept94)Comment: 12 pages, uuencoded compressed Postscript fil
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Subaru Studies of the Cosmic Dawn
An overview on the current status of the census of the early universe
population is given. Observational surveys of high redshift objects provide
direct opportunities to study the early epoch of the Universe. The target
population included are Lyman Alpha Emitters (LAE), Lyman Break Galaxies (LBG),
gravitationally lensed galaxies, quasars and gamma-ray bursts (GRB). The basic
properties of these objects and the methods used to study them are reviewed.
The present paper highlights the fact that the Subaru Telescope group made
significant contributions in this field of science to elucidate the epoch of
the cosmic dawn and to improve the understanding of how and when infant
galaxies evolve into mature ones.Comment: 14 pages, 11 figures, accepted for publication in the Proceedings of
the Japan Academy, Series
The CNOC2 field galaxy redshift survey
The second Canadian Network for Observational Cosmology ( CNOC) galaxy redshift survey, CNOC2, is designed to investigate the relations between the dramatic evolution of field galaxies and their clustering over the redshift range 0 to 0.7. The sample of about 6000 galaxies with accurate velocities is spread over four sky patches with a total area of about 1.5deg2. Here we report preliminary results based on two of the sky patches and within the redshift range of 0.12 to 0.55. After classifying the galaxy spectral energy distributions relative to nonâevolving references, we find that the early and intermediateâtype populations can be described with nearly pure luminosity evolution, whereas the lateâtype population requires nearly pure density evolution. The spatial twoâpoint correlation functions have a strong colour dependence with scale, and a weaker, apparently scaleâfree, luminosity dependence. The population most likely to be conserved with redshift is the highâluminosity galaxies. In particular, we choose galaxies with MRke â©œâ20 mag as our tracer population. We find that the evolution of the clustered density in proper coâordinates at r âČ 10hâ1 Mpc, Ïgg â r0Îł(1+z)3, is best described as a âdeâclusteringâ, proportional to (1+z)0.6±0.4); or equivalently, there is a weak growth of clustering in coâmoving coâordinates, x0 â(1+z)(â0.3±0.2). This conclusion is supported by the pairwise peculiar velocities, which show no significant change with redshift. The cosmic virial theorem applied to the CNOC2 data gives Q3ΩM/b = 0.11 ± 0.04, where Q3 is the threeâpoint correlation parameter and b the bias
Results on Galaxy Evolution from the CNOC2 Field Galaxy Redshift Survey
The CNOC2 Field Galaxy Redshift Survey presently contains some 5000 galaxy redshifts, plus extensive UBgRI photometry, and is the largest galaxy sample at moderate redshifts 0.1 < z < 0.6. Here we present some preliminary results on the galaxy luminosity function (LF) and its redshift evolution, using a sample of R < 21.5 CNOC2 galaxies, subdivided into early, intermediate, and late types based on their B-R colors relative to non-evolving galaxy models. We find a significant steepening in the faint-end slope alpha of the LF as one proceeds from early to late types. Also, for all galaxy types we find a rate of M* evolution consistent with that from passively evolving galaxy models. Finally, late-type galaxies show positive density evolution with redshift, in contrast to negative or no density evolution for earlier types