360 research outputs found
The UNAM-KIAS Catalog of Isolated Galaxies
A new catalog of isolated galaxies from The Sloan Digital Sky Survey (DR5) is
presented. 1520 isolated galaxies were found in 1.4 steradians of sky. The
selection criteria in this so called UNAM-KIAS catalog was implemented from a
variation on the criteria developed by Karachentseva 1973 including full
redshift information. Through an image processing pipeline that takes advantage
from the high resolution (~ 0.4 ''/pix) and high dynamic range of the SDSS
images, a uniform g band morphological classification for all these galaxies is
presented. We identify 80% (SaSm) spirals (50% later than Sbc types) on one
hand, and a scarce population of early-type E(6.5%) and S0(8%) galaxies
amounting to 14.5% on the other hand. This magnitude-limited catalog is ~ 80%
complete at 16.5, 15.6, 15.0, 14.6 and 14.4 magnitudes in the ugriz bands
respectively. Some representative physical properties including SDSS magnitudes
and color distributions, color-color diagrams, absolute magnitude-color, and
concentration-color diagrams as a function of morphological type are presented.
The UNAM-KIAS Morphological Atlas is also released along with this paper. For
each galaxy of type later than Sa, a mosaic is presented that includes: (1) a
g-band logarithmic image, (2) a g band filtered-enhanced image where a Gaussian
kernel of various sizes was applied and (3) an RGB color image from the SDSS
database. For E/S0/Sa galaxies, in addition to the images in (1), (2) and (3),
plots of r band surface brightness and geometric profiles (ellipticity,
Position Angle PA and A4/B4 coefficients of the Fourier series expansions of
deviations of a pure ellipse) are provided...Comment: 40 pages, 17 figures and 3 table
The UNAM-KIAS Catalog of Isolated Galaxies
A new catalog of isolated galaxies from The Sloan Digital Sky Survey (DR5) is
presented. 1520 isolated galaxies were found in 1.4 steradians of sky. The
selection criteria in this so called UNAM-KIAS catalog was implemented from a
variation on the criteria developed by Karachentseva 1973 including full
redshift information. Through an image processing pipeline that takes advantage
from the high resolution (~ 0.4 ''/pix) and high dynamic range of the SDSS
images, a uniform g band morphological classification for all these galaxies is
presented. We identify 80% (SaSm) spirals (50% later than Sbc types) on one
hand, and a scarce population of early-type E(6.5%) and S0(8%) galaxies
amounting to 14.5% on the other hand. This magnitude-limited catalog is ~ 80%
complete at 16.5, 15.6, 15.0, 14.6 and 14.4 magnitudes in the ugriz bands
respectively. Some representative physical properties including SDSS magnitudes
and color distributions, color-color diagrams, absolute magnitude-color, and
concentration-color diagrams as a function of morphological type are presented.
The UNAM-KIAS Morphological Atlas is also released along with this paper. For
each galaxy of type later than Sa, a mosaic is presented that includes: (1) a
g-band logarithmic image, (2) a g band filtered-enhanced image where a Gaussian
kernel of various sizes was applied and (3) an RGB color image from the SDSS
database. For E/S0/Sa galaxies, in addition to the images in (1), (2) and (3),
plots of r band surface brightness and geometric profiles (ellipticity,
Position Angle PA and A4/B4 coefficients of the Fourier series expansions of
deviations of a pure ellipse) are provided...Comment: 40 pages, 17 figures and 3 table
The Bulgeless Seyfert/LINER Galaxy NGC 3367: Disk, Bar, Lopsidedness and Environment
NGC3367 is a nearby isolated active galaxy that shows a radio jet, a strong
bar and evidence of lopsidedness. We present a quantitative analysis of the
stellar and gaseous structure of the galaxy disk and a search for evidence of
recent interaction based on new UBVRI Halpha and JHK images and on archival
Halpha Fabry-Perot and HI VLA data. From a coupled 1D/2D GALFIT bulge/bar/disk
decomposition an (B/D ~ 0.07-0.1) exponential pseudobulge is inferred in all
the observed bands. A NIR estimate of the bar strength = 0.44
places NGC 3367 bar among the strongest ones. The asymmetry properties were
studied using (1) optical and NIR CAS indexes (2) the stellar (NIR) and gaseous
(Halpha, HI) A_1 Fourier mode amplitudes and (3) the HI integrated profile and
HI mean intensity distribution. While the average stellar component shows
asymmetry values close to the average found in the Local Universe for isolated
galaxies, the young stellar component and gas values are largely decoupled
showing significantly larger A_1 mode amplitudes suggesting that the gas has
been recently perturbed. Our search for (1) faint stellar structures in the
outer regions (up to u_R ~ 26 mag arcsec^{-2}), (2) (Halpha) star-forming
satellite galaxies and (3) regions with different colors (stellar populations)
along the disk all failed. Such an absence is interpreted using recent
numerical simulations to constrain a tidal event with an LMC like galaxy to
some dynamical times in the past or to a current very low mass, gas rich
accretion. We conclude that a cold accretion mode (gas and small/dark galaxies)
may be responsible of the nuclear activity and peculiar (young stars and gas)
morphology regardless of the highly isolated environment. Black hole growth in
bulgeless galaxies may be triggered by cosmic smooth mass accretion.Comment: 27 pages, 12 figures, accepted for publication in The Astronomical
Journa
BVRI Surface Photometry of (S+S) Binary Galaxies. I. The data
We present multicolour broad band () photometry for a sample of 33
spiral-spiral (S+S) binary galaxies drawn from the Karachentsev Catalogue of
Isolated Pairs of Galaxies (KPG). The data is part of a joint observational
programme devoted to systematic photometric study of one of the most complete
and homogeneous pair samples available in the literature. We present
azimuthally averaged colour and surface brightness profiles, colour index (B-I)
maps, B band and sharp/filtered B band images as well as integrated magnitudes,
magnitudes at different circular apertures and integrated colours for each
pair. Internal and external data comparisons show consistency within the
estimated errors. Two thirds of the sample have total aperture parameters
homogeneously derived for the first time. After reevaluating morphology for all
the pairs, we find a change in Hubble type for 24 galaxies compared to the
original POSS classifications. More than half of our pairs show morphological
concordance which could explain, in part, the strong correlation in the (B-V)
colour indices (Holmberg Effect) between pair components. We find a tendency
for barred galaxies to show grand design morphologies and flat colour profiles.
The measurements will be used in a series of forthcoming papers where we try to
identify and isolate the main structural and photometric properties of disk
galaxies at different stages of interaction.Comment: 23 pages. 5 Figures. Accepted for publication in Astronomy and
Astrophysics. Mosaics for all pairs can be found at
http://www.inaoep.mx/~puerari/binar
BVRI Surface Photometry of Isolated Spiral Galaxies
A release of multicolor broad band (BVRI) photometry for a subsample of 44
isolated spirals drawn from the Catalogue of Isolated Galaxies (CIG) is
presented. Total magnitudes and colors at various circular apertures, as well
as some global structural/morphological parameters are estimated. Morphology is
reevaluated through optical and sharp/filtered R band images, (B-I) color index
maps, and archive near-IR JHK images from the Two-Micron Survey. The CAS
structural parameters (Concentration, Asymmetry, and Clumpiness) were
calculated from the images in each one of the bands. The fraction of galaxies
with well identified optical/near-IR bars (SB) is 63%, while a 17% more shows
evidence of weak or suspected bars (SAB). The sample average value of the
maximum bar ellipticity is 0.4. Half of the galaxies in the sample shows rings.
We identify two candidates for isolated galaxies with disturbed morphology. The
structural CAS parameters change with the observed band, and the tendencies
they follow with the morphological type and global color are more evident in
the redder bands. In any band, the major difference between our isolated
spirals and a sample of interacting spirals is revealed in the A-S plane. A
deep and uniformly observed sample of isolated galaxies is intended for various
purposes including (i) comparative studies of environmental effects, (ii)
confronting model predictions of galaxy evolution and (iii) evaluating the
change of galaxy properties with redshift.Comment: 44 pages, 9 figures and 7 tables included. To appear in The
Astronomical Journal. For the 43 appendix figures 4.1-4.43 see
http://www.astroscu.unam.mx/~avila/Figs4.1_4.43.tar.gz (7.2 Mb tar.gz file
Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA. VI. The role of bars in quenching star formation from z = 3 to the present epoch
A growing body of evidence indicates that the star formation rate per unit stellar mass (sSFR) decreases with increasing mass in normal main-sequence star-forming galaxies. Many processes have been advocated as being responsible for this trend (also known as mass quenching), e.g., feedback from active galactic nuclei (AGNs), and the formation of classical bulges. In order to improve our insight into the mechanisms regulating the star formation in normal star-forming galaxies across cosmic epochs, we determine a refined star formation versus stellar mass relation in the local Universe. To this end we use the Hα narrow-band imaging follow-up survey (Hα3) of field galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Coma and Local superclusters. By complementing this local determination with high-redshift measurements from the literature, we reconstruct the star formation history of main-sequence galaxies as a function of stellar mass from the present epoch up to z = 3. In agreement with previous studies, our analysis shows that quenching mechanisms occur above a threshold stellar mass Mknee that evolves with redshift as ∝ (1 + z)2. Moreover, visual morphological classification of individual objects in our local sample reveals a sharp increase in the fraction of visually classified strong bars with mass, hinting that strong bars may contribute to the observed downturn in the sSFR above Mknee. We test this hypothesis using a simple but physically motivated numerical model for bar formation, finding that strong bars can rapidly quench star formation in the central few kpc of field galaxies. We conclude that strong bars contribute significantly to the red colors observed in the inner parts of massive galaxies, although additional mechanisms are likely required to quench the star formation in the outer regions of massive spiral galaxies. Intriguingly, when we extrapolate our model to higher redshifts, we successfully recover the observed redshift evolution for Mknee. Our study highlights how the formation of strong bars in massive galaxies is an important mechanism in regulating the redshift evolution of the sSFR for field main-sequence galaxies
- …