145 research outputs found
Evolution of the Fundamental Plane of 0.2<z<1.2 Early-type galaxies in the EGS
The Fundamental Plane relates the structural properties of early-type
galaxies such as its surface brightness and effective radius with its dynamics.
The study of its evolution has therefore important implications for models of
galaxy formation and evolution. This work aims to identify signs of evolution
of early-type galaxies through the study of parameter correlations using a
sample of 135 field galaxies extracted from the Extended Groth Strip in the
redshift range 0.2<z<1.2. Using DEEP2 data, we calculate the internal velocity
dispersions by extracting the stellar kinematics from absorption line spectra,
using a maximum penalized likelihood approach. Morphology was determined
through visual classification using the V+I images of ACS. The structural
parameters of these galaxies were obtained by fitting de Vaucouleurs stellar
profiles to the ACS I-band images, using the GALFIT code. S\'ersic and
bulge-to-disc decomposition models were also fitted to our sample of galaxies,
and we found a good agreement in the Fundamental Plane derived from the three
models. Assuming that effective radii and velocity dispersions do not evolve
with redshift, we have found a brightening of 0.68 mag in the B-band and 0.52
mag in the g-band at =0.7. However, the scatter in the FP is reduced by half
when we allow the FP slope to evolve, suggesting a different evolution of
early-type galaxies according to their intrinsic properties. The study of the
Kormendy relation shows the existence of a population of very compact (Re<2
Kpc) and bright galaxies (-21.5>Mg>-22.5), of which there are only a small
fraction (0.4%) at z=0. The evolution of these compact objects is mainly caused
by an increase in size that could be explained by the action of dry minor
mergers, and this population is responsible for the evolution detected in the
Fundamental Plane.Comment: Accepted for publication in A&A. 12 pages, 10 Figures, and 1 online
tabl
Spatially-resolved spectrophotometric analysis and modelling of the Superantennae
We have performed spatially-resolved spectroscopy of the double-nucleated
Ultra-Luminous Infrared Galaxy IRAS 19254-7245, ``the Superantennae'', along
the line connecting the two nuclei. These data are analysed with a spectral
synthesis code, to derive the star formation and extinction properties of the
galaxy. The star formation history (SFH) of the two nuclei is similarly
characterized by two different main episodes: a recent burst, responsible of
the observed emission lines, and an older one, occurred roughly 1 Gyr ago. We
tentatively associate this bimodal SFH with a double encounter in the dynamical
history of the merger. We have complemented our study with a detailed analysis
of the broad band spectral energy distribution of the Superantennae, built from
published photometry, providing the separate optical-to-mm SEDs of the two
nuclei. Our analysis shows that: a) the southern nucleus is responsible for
about 80% of the total infrared luminosity of the system, b) the L-band
luminosity in the southern nucleus is dominated by the emission from an
obscured AGN, providing about 40 to 50% of the bolometric flux between 8 and
1000 microns; c) the northern nucleus does not show evidence for AGN emission
and appears to be in a post-starburst phase. As for the relative strengths of
the AGN and starburst components, we find that, while they are comparable at
FIR and sub-mm wavelengths, in the radio the Sy2 emission dominates by an order
of magnitude the starburst.Comment: 18 pages. Accepted for publication on A&
The Kormendy Relation for early-type galaxies. Dependence on the magnitude range
Previous studies indicate that faint and bright early-type galaxies (ETGs)
present different coefficients and dispersion for their Kormendy relation (KR).
A recently published paper states that the intrinsic dispersion of the KR
depends on the magnitude range within which the galaxies are contained,
therefore, we investigate here whether the magnitude range has also an
influence over the values of the coefficients of the KR; (zero point)
and (slope). We perform numerical simulations and analysis of these
coefficients for 4 samples of galaxies, which contain an approximate total of
9400 ETGs in a relatively ample magnitude range ( ).
The analysis of the results makes us conclude that the values of the KR
coefficients depend on the width of the magnitude range and the brightness of
galaxies within the magnitude range. This dependence is due to the fact that
the distribution of galaxies in the plane depends on
luminosity and that this distribution is not symmetrical, that is, the
geometric shape of the distribution of galaxies in the plane plays an important role in the determination of the values of
the coefficients of the KR.Comment: 22 pages, 10 figures. A&A. Accepte
The Mass of HD 38529 c from Hubble Space Telescope Astrometry and High-Precision Radial Velocities
(Abridged) Hubble Space Telescope (HST) Fine Guidance Sensor astrometric
observations of the G4 IV star HD 38529 are combined with the results of the
analysis of extensive ground-based radial velocity data to determine the mass
of the outermost of two previously known companions. Our new radial velocities
obtained with the Hobby-Eberly Telescope and velocities from the
Carnegie-California group now span over eleven years. With these data we obtain
improved RV orbital elements for both the inner companion, HD 38529 b and the
outer companion, HD 38529 c. We identify a rotational period of HD 38529
(P_{rot}=31.65 +/- 0.17 d) with FGS photometry. We model the combined
astrometric and RV measurements to obtain the parallax, proper motion,
perturbation period, perturbation inclination, and perturbation size due to HD
38529 c. For HD 38529 c we find P = 2136.1 +/- 0.3 d, perturbation semi-major
axis \alpha =1.05 +/-0.06i_{Jup}) companion at
P~194 days. Additional observations (radial velocities and/or Gaia astrometry)
are required to validate an interpretation of HD 38529 d as a planetary-mass
companion. If confirmed, the resulting HD 38529 planetary system may be an
example of a "Packed Planetary System".Comment: Accepted by The Astronomical Journa
Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
We combine VI photometry from OGLE-III with VVV and 2MASS measurements of
E(J-K_{s}) to resolve the longstanding problem of the non-standard optical
extinction toward the Galactic bulge. We show that the extinction is well-fit
by the relation A_{I} = 0.7465*E(V-I) + 1.3700*E(J-K_{s}), or, equivalently,
A_{I} = 1.217*E(V-I)(1+1.126*(E(J-K_{s})/E(V-I)-0.3433)). The optical and
near-IR reddening law toward the inner Galaxy approximately follows an R_{V}
\approx 2.5 extinction curve with a dispersion {\sigma}_{R_{V}} \approx 0.2,
consistent with extragalactic investigations of the hosts of type Ia SNe.
Differential reddening is shown to be significant on scales as small as as our
mean field size of 6', with the 1{\sigma} dispersion in reddening averaging 9%
of total reddening for our fields. The intrinsic luminosity parameters of the
Galactic bulge red clump (RC) are derived to be (M_{I,RC}, \sigma_{I,RC,0},
(V-I)_{RC,0}, \sigma_{(V-I)_{RC}}, (J-K_{s})_{RC,0}) = (-0.12, 0.09, 1.06,
0.121, 0.66). Our measurements of the RC brightness, brightness dispersion and
number counts allow us to estimate several Galactic bulge structural
parameters. We estimate a distance to the Galactic center of 8.20 kpc,
resolving previous discrepancies in distance determinations to the bulge based
on I-band observations. We measure an upper bound on the tilt {\alpha} \approx
40{\deg}. between the bar's major axis and the Sun-Galactic center line of
sight, though our brightness peaks are consistent with predictions of an N-body
model oriented at {\alpha} \approx 25{\deg}. The number of RC stars suggests a
total stellar mass for the Galactic bulge of 2.0*10^{10} M_{\odot}, if one
assumes a Salpeter IMF.Comment: 61 Pages, 21 Figures, 4 Tables, Submitted to The Astrophysical
Journal and modified as per a referee report. Includes reddening, reddening
law, differential reddening, mean distance, dispersion in distance, surface
density of stars and errors thereof for ~9,000 bulge sightlines. For a brief
video explaining the key result of this paper, see
http://www.youtube.com/user/OSUAstronom
The mass distribution of RX J1347-1145 from strong lensing
High resolution HST/ACS images of the galaxy cluster RX J1347-1145 have
enabled us to identify several new multiple image candidates in the cluster,
including a 5 image system with a central image. The multiple images allow us
to construct an accurate 2-dimensional mass map of the central part of the
cluster. The modelling of the cluster mass includes the most prominent cluster
galaxies modelled as truncated isothermal spheres and a smooth halo component
that is described with 2 parametric profiles. The mass reconstruction is done
using a Markov chain Monte Carlo method that provides us with a total projected
mass density as well as estimates for the parameters of interest and their
respective errors. The mass profile is in reasonable agreement with previous
mass estimates based on the X-ray emission from the hot intra-cluster gas,
however the X-ray mass estimates are systematically lower than what we obtain
with gravitational lensing.Comment: Accepted for publication in the A&
Data and 2D scaling relations for galaxies in Abell 1689: a hint of size evolution at z~0.2
{abridged} We present imaging and spectroscopy of Abell 1689 (z=0.183) from
GEMINI/GMOS-N and HST/ACS. We measure integrated photometry from the GMOS g'
and r' images (for 531 galaxies) and surface photometry from the HST F625W
image (for 43 galaxies) as well as velocities and velocity dispersions from the
GMOS spectra (for 71 galaxies). We construct the Kormendy relation (KR),
Faber-Jackson relation (FJR) and colour-magnitude relation (CMR) for early-type
galaxies in Abell 1689 using this data and compare them to those of the Coma
cluster. We measure the intrinsic scatter of the CMR in Abell 1689 to be 0.054
\pm 0.004 mag which places degenerate constraints on the ratio of the assembly
timescale to the time available (beta) and the age of the population. Making
the assumption that galaxies in Abell 1689 will evolve into those of Coma over
an interval of 2.26 Gyr breaks this degeneracy and limits beta to be > 0.6 and
the age of the red sequence to be > 5.5 Gyr (formed at z > 0.55). Without
corrections for size evolution but accounting for magnitude cuts and selection
effects, the KR & FJR are inconsistent and disagree at the 2 sigma level
regarding the amount of luminosity evolution in the last 2.26 Gyr. However,
after correcting for size evolution the KR & FJR show similar changes in
luminosity (0.22 \pm 0.11 mag) that are consistent with the passive evolution
of the stellar populations from a single burst of star formation 10.2 \pm 3.3
Gyr ago (z = 1.8+inf-0.9). Thus the changes in the KR, FJR & CMR of Abell 1689
relative to Coma all agree and suggest old galaxy populations with little or no
synchronisation in the star formation histories. Furthermore, the weak evidence
for size evolution in the cluster environment in the last 2.26 Gyr places
interesting constraints on the possible mechanisms at work, favouring
harassment or secular processes over merger scenarios.Comment: Accepted for publication in MNRA
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
Astronometry with the Hubble Space Telescope : trigonometric parallaxes of planetary nebula nuclei NGC 6853, NGC 7293, Abell 31 and DeHt 5
Original article can be found at: http://www.iop.org/EJ/journal/1538-3881 Copyright American Astronomical Society. DOI: 10.1088/0004-6256/138/6/1969We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1r and FGS 3, white-light interferometers on the Hubble Space Telescope. Proper motions, spectral classifications and VJHKT2M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, σπ/π = 5%. Derived distances are: d NGC 6853 = 405+28 –25 pc, d NGC 7293 = 216+14 –12 pc, d Abell 31 = 621+91 –70 pc, and d DeHt 5 = 345+19 –17 pc. These PNNi distances are all smaller than previously derived from spectroscopic analyses of the central stars. To obtain absolute magnitudes from these distances requires estimates of interstellar extinction. We average extinction measurements culled from the literature, from reddening based on PNNi intrinsic colors derived from model SEDs, and an assumption that each PNN experiences the same rate of extinction as a function of distance as do the reference stars nearest (in angular separation) to each central star. We also apply Lutz-Kelker bias corrections. The absolute magnitudes and effective temperatures permit estimates of PNNi radii through both the Stefan-Boltzmann relation and Eddington fluxes. Comparing absolute magnitudes with post-AGB models provides mass estimates. Masses cluster around 0.57 , close to the peak of the white dwarf mass distribution. Adding a few more PNNi with well-determined distances and masses, we compare all the PNNi with cooler white dwarfs of similar mass, and confirm, as expected, that PNNi have larger radii than white dwarfs that have reached their final cooling tracks.Peer reviewe
The Sloan Digital Sky Survey-II: Photometry and Supernova Ia Light Curves from the 2005 data
We present ugriz light curves for 146 spectroscopically confirmed or
spectroscopically probable Type Ia supernovae from the 2005 season of the
SDSS-II Supernova survey. The light curves have been constructed using a
photometric technique that we call scene modelling, which is described in
detail here; the major feature is that supernova brightnesses are extracted
from a stack of images without spatial resampling or convolution of the image
data. This procedure produces accurate photometry along with accurate estimates
of the statistical uncertainty, and can be used to derive photometry taken with
multiple telescopes. We discuss various tests of this technique that
demonstrate its capabilities. We also describe the methodology used for the
calibration of the photometry, and present calibrated magnitudes and fluxes for
all of the spectroscopic SNe Ia from the 2005 season
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