100 research outputs found
Multi-component parametric inversion of galaxy kinematics and stellar populations using full spectral fitting
The stellar line-of-sight velocity distribution (LOSVD) can be strongly
asymmetric in regions where the light contributions of both disc and bulge in
spiral and lenticular galaxies are comparable. Existing techniques for the
stellar kinematics analysis do not take into account the difference of disc and
bulge stellar populations. Here we present a novel approach to the analysis of
stellar kinematics and stellar populations. We use a two-component model of
spectra where different stellar population components are convolved with pure
Gaussian LOSVDs. For this model we present Monte-Carlo simulations
demonstrating degeneracies between the parameters.Comment: 3 pages, 2 figures; to appear in the proceedings of "The Spectral
Energy Distribution of Galaxies", Preston, UK, 5-9 September 201
Analytical approximations of K-corrections in optical and near-infrared bands
To compare photometric properties of galaxies at different redshifts, the
fluxes need to be corrected for the changes of effective rest-frame wavelengths
of filter bandpasses, called K-corrections. Usual approaches to compute them
are based on the template fitting of observed spectral energy distributions
(SED) and, thus, require multi-colour photometry. Here, we demonstrate that, in
cases of widely used optical and near-infrared filters, K-corrections can be
precisely approximated as two-dimensional low-order polynomials of only two
parameters: redshift and one observed colour. With this minimalist approach, we
present the polynomial fitting functions for K-corrections in SDSS ugriz, UKIRT
WFCAM YJHK, Johnson-Cousins UBVR_cI_c, and 2MASS JHK_s bands for galaxies at
redshifts Z<0.5 based on empirically-computed values obtained by fitting
combined optical-NIR SEDs of a set of 10^5 galaxies constructed from SDSS DR7
and UKIDSS DR5 photometry using the Virtual Observatory. For luminous red
galaxies we provide K-corrections as functions of their redshifts only. In two
filters, g and r, we validate our solutions by computing K-corrections directly
from SDSS DR7 spectra. We also present a K-corrections calculator, a web-based
service for computing K-corrections on-line.Comment: 13 pages, 7 figures, 25 tables. Accepted for publication in MNRAS.
This version contains low-resolution figures. The "K-corrections calculator"
service is available at http://kcor.sai.msu.ru
NBursts+phot: parametric recovery of galaxy star formation histories from the simultaneous fitting of spectra and broad-band spectral energy distributions
We present NBursts+phot, a novel technique for the parametric inversion of
spectrophotometric data for unresolved stellar populations where
high-resolution spectra and broadband SEDs are fitted simultaneously helping to
break the degeneracies between parameters of multi-component stellar population
models.Comment: 3 pages, 1 figure, proceedings of the IAU Symposium 28
The matter distribution in the local Universe as derived from galaxy groups in SDSS DR12 and 2MRS
Context. Friends-of-friends algorithms are a common tool to detect galaxy
groups and clusters in large survey data. In order to be as precise as
possible, they have to be carefully calibrated using mock catalogues.
Aims. We create an accurate and robust description of the matter distribution
in the local Universe using the most up-to-date available data. This will
provide the input for a specific cosmological test planned as follow-up to this
work, and will be useful for general extragalactic and cosmological research.
Methods. We created a set of galaxy group catalogues based on the 2MRS and
SDSS DR12 galaxy samples using a friends-of-friends based group finder
algorithm. The algorithm was carefully calibrated and optimised on a new set of
wide-angle mock catalogues from the Millennium simulation, in order to provide
accurate total mass estimates of the galaxy groups taking into account the
relevant observational biases in 2MRS and SDSS.
Results. We provide four different catalogues (i) a 2MRS based group
catalogue; (ii) an SDSS DR12 based group catalogue reaching out to a redshift z
= 0.11 with stellar mass estimates for 70% of the galaxies; (iii) a catalogue
providing additional fundamental plane distances for all groups of the SDSS
catalogue that host elliptical galaxies; (iv) a catalogue of the mass
distribution in the local Universe based on a combination of our 2MRS and SDSS
catalogues.
Conclusions. While motivated by a specific cosmological test, three of the
four catalogues that we produced are well suited to act as reference databases
for a variety of extragalactic and cosmological science cases. Our catalogue of
fundamental plane distances for SDSS groups provides further added value to
this paper.Comment: 31 pages, 25 figures, accepted for publication in A&
SDSSJ150634.27+013331.6: the second compact elliptical galaxy in the NGC5846 group
We report the discovery of the second compact elliptical (cE) galaxy
SDSSJ150634.27+013331.6 in the nearby NGC5846 group by the Virtual Observatory
(VO) workflow . This object (M_B = -15.98 mag, R_e = 0.24 kpc) becomes the
fifth cE where the spatially-resolved kinematics and stellar populations can be
obtained. We used archival HST WFPC2 images to demonstrate that its light
profile has a two-component structure, and integrated photometry from GALEX,
SDSS, UKIDSS, and Spitzer to build the multi-wavelength SED to constraint the
star formation history (SFH). We observed this galaxy with the PMAS IFU
spectrograph at the Calar-Alto 3.5m telescope and obtained two-dimensional maps
of its kinematics and stellar population properties using the full-spectral
fitting technique. Its structural, dynamical and stellar population properties
suggest that it had a massive progenitor heavily tidally stripped by NGC5846.Comment: 5 pages, 4 figure, 1 table. Accepted to MNRAS Letter
- âŠ