We have imaged the recently discovered stellar overdensity located approximately one core radius from the center of the Fornax dwarf spheroidal galaxy using the Magellan Clay 6.5m telescope with the Magellan Instant Camera. Superb seeing conditions allowed us to probe the stellar populations of this overdensity and of a control field within Fornax to a limiting magnitude of R=26. The color-magnitude diagram of the overdensity field is virtually identical to that of the control field, with the exception of the presence of a population arising from a very short (less than 300Myr in duration) burst of star formation 1.4Gyr ago.
We carried out CCD photometry in the Johnson-Cousins B and R bands of 23 dwarf galaxies: SDIG, ESO 410-17, KK11, ESO 245-05, KKs3, KK27, KK38, KK40, IC 4662, KK244, KK246, KK247, KK248, KK249, KK253, KK255, KK256, KK257, KK258, KK259, UGCA 438, ESO 347-17, and UGCA 442. Both isolated galaxies and members of the Sculptor group and the NGC 1313 group were observed. The galaxy sample is characterized by a median distance of 9.3Mpc, and median absolute magnitude of -14.8mag. The central surface brightnesses are in the range from 22.2 to 24.4mag/arcsec^2^ in B.
We present the results of a photometric and spectroscopic study of seven members of the NGC 5328 group of galaxies, a chain of galaxies spanning over 200kpc (H0=70km/s/Mpc). We analyse the galaxy structure and study the emission-line properties of the group members looking for signatures of star formation and active galactic nucleus activity. We finally attempt to infer, from the modelling of line-strength indices, the stellar population ages of the early-type members.
File table3 contains a summary of selected B and R photometry data for 72 irregular dwarf galaxies within the 10 Mpc volume. It is supplemented by the indication of their field or group membership and by their rotational velocities as inferred from the literature.
B and R CCD images and J NICMOS3 frames taken with the Calar Alto 3.5m telescope of the dwarf irregular galaxy UGC 685 are presented. The brightest part of the stellar population is resolved in B and R, very few also in J. The stellar color-magnitude diagram is discussed. An estimate of the distance to UGC 685 of 5. 5Mpc is derived based on the brightest blue supergiant stars. Most of the resolved bright stars show colors in the range -0.1<=B-R<=+0.7.
Detailed B and R surface photometry is performed for 139 faint emission-line galaxies (ELGs) and for 2 non-ELGs. They are a subsample of the ELG sample selected by Popescu et al. (1996A&AS..116...43P, 1998A&AS..133...13P) towards four nearby voids. We derived the isophotal and integral photometric parameters and radial surface brightness (SB) profiles. Our sample consists mostly of low luminosity (<M_B_>_med_=-17.7), small linear size (<d_25_>_med_=6.0kpc) (H_0_=75km/s/Mpc) and blue (<B-R>_med_=0.93) galaxies. About 83% of the studied ELGs belong to the class of Blue Compact Galaxies (BCGs); others are luminous Starburst Nucleus Galaxies (SBNs) and a few interacting pairs. 72% of the ELGs possess a single dominant H II region, while the remaining 28% show multiple knots. Furthermore 71% of the ELGs show regular outer isophotes, and the remaining 29% reveal disturbed outer morphologies.
We have performed 2D bulge/bar/disc decompositions using g, r and i-band images of a representative sample of nearly 1000 galaxies from the Sloan Digital Sky Survey. We show that the Petrosian concentration index is a better proxy for the bulge-to-total ratio than the global Sersic index. We show that pseudo-bulges can be distinguished from classical bulges as outliers in the Kormendy relation. We provide the structural parameters and distributions of stellar masses of ellipticals, classical bulges, pseudo-bulges, discs and bars, and find that 32% of the total stellar mass in massive galaxies in the local universe is contained in ellipticals, 36% in discs, 25% in classical bulges, 3% in pseudo-bulges and 4% in bars.
We present the optical spectroscopy for the Blind Ultra Deep HI Environmental Survey (BUDHIES). With the Westerbork Synthesis Radio Telescope, BUDHIES has detected HI in over 150 galaxies in and around two Abell clusters at z=~0.2. With the aim of characterizing the environments of the Hi-detected galaxies, we obtained multifibre spectroscopy with the William Herschel Telescope. In this paper, we describe the spectroscopic observations, report redshifts and EW[OII] measurements for ~600 galaxies, and perform an environmental analysis. In particular, we present cluster velocity dispersion measurements for five clusters and groups in the BUDHIES volume, as well as a detailed substructure analysis.
We explore the internal structure of red-sequence galaxies in the Coma cluster across a wide range of luminosities (-17>M_g_>-22) and cluster-centric radii (0<r_cluster_<1.3r_200_). We present the 2D bulge-disc decomposition of galaxies in deep Canada-France-Hawaii Telescope u, g, i imaging using GALFIT. Rigorous filtering is applied to identify an analysis sample of 200 galaxies which are well described by an 'archetypal' S0 structure (central bulge + outer disc).
We perform two-dimensional, point-spread-function-convolved, bulge+disk decompositions in the g and r bandpasses on a sample of 1123718 galaxies from the Legacy area of the Sloan Digital Sky Survey Data Release Seven. Four different decomposition procedures are investigated which make improvements to sky background determinations and object deblending over the standard SDSS procedures that lead to more robust structural parameters and integrated galaxy magnitudes and colors, especially in crowded environments. We use a set of science-based quality assurance metrics, namely, the disk luminosity-size relation, the galaxy color-magnitude diagram, and the galaxy central (fiber) colors to show the robustness of our structural parameters. The best procedure utilizes simultaneous, two-bandpass decompositions. Bulge and disk photometric errors remain below 0.1mag down to bulge and disk magnitudes of g~19 and r~18.5. We also use and compare three different galaxy fitting models: a pure Sersic model, an n_b_=4 bulge+disk model, and a Sersic (free n_b_) bulge+disk model. The most appropriate model for a given galaxy is determined by the F-test probability. All three catalogs of measured structural parameters, rest-frame magnitudes, and colors are publicly released here.
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