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.
In this paper we report the multi-band BVRI photometry of HD 52452. The comparison of our data with previous observations reported by Messina et al. (2001) shows that there is a variation in amplitude, but the phases of the two minima, thus the positions of the spot, are quite stable during our observations.
We report the first results of our multicolour broad-band BVRI photometry for a statistically well defined sample of interacting pairs, drawn from the Catalogue of Isolated Pairs of Galaxies in the Northern Hemisphere Karachentsev (1972). At present, the details of photometric structure of disk-disk (S+S) galaxies are just beginning to be studied because of their intrinsic difficulties. We take advantage of the statistical properties of this well defined sample of interacting galaxies to try to isolate the main structural components of galaxies. Due to their environmental simplicity (compared …
Detailed BVRI-Halpha photometry has been obtained for the ring galaxy HRG 2302. This is probably a still interacting system which shows two principal components: the target, which is a knotted ringed-disk, and the intruder, an elongated galaxy with two substructures probably caused by the interaction. The existence of H II emission regions is suggested by Halpha images and medium dispersion spectra of the three brightest parts of this system. Analysis of a color-color diagram suggests recent star formation, in agreement with the behavior of interacting galaxies with nuclear emission. HRG 2302 …
CCD observations of the gravitational lens system Q0957+561A,B in the BVRI bands are presented in this paper. The observations, taken with the 82 cm IAC-80 telescope, at Teide Observatory, Spain, were made from the beginning of 1996 February to 1998 July, as part of an on-going lens monitoring program. Accurate photometry was obtained by simultaneously fitting a stellar two-dimensional profile on each component by means of DAOPHOT software. This alternative method equals and even improves the results obtained with previous techniques. The final dataset is characterized by its high degree of ho…
We report BV(RI)c CCD photometric data for a group of seven Cepheid variables in the young, rich cluster NGC 1866 in the Large Magellanic Cloud. The photometry was obtained as part of a program to determine accurate distances to these Cepheids by means of the infrared surface brightness technique, and to improve the LMC Cepheid database for constructing Cepheid PL and PLC relations. Using the new data together with data from the literature, we have determined improved periods for all variables. For five fundamental mode pulsators, the light curves are now of excellent quality and will lead to …
The CCD magnitudes in Johnson $BV$ and Cousins $RI$ photometric passbands are determined for 18 stars in the field of GRB 990123. These measurements can be used in carrying out precise CCD photometry of the optical transient of GRB 990123 using differential photometric techniques during non--photometric sky conditions. A comparison with previous photometry indicates that the present photmetry is more precise.
We present optical photometry of one Type IIn supernova (1994Y) and nine Type Ia supernovae (1993Y, 1993Z, 1993ae, 1994B, 1994C, 1994M, 1994Q, 1994ae, and 1995D). SN 1993Y and SN 1993Z appear to be normal SN Ia events with similar rates of decline, but we do not have data near maximum brightness. The colors of SN 1994C suggest that it suffers from significant reddening or is intrinsically red. The light curves of SN 1994Y are complicated; they show a slow rise and gradual decline near maximum brightness in $VRI$ and numerous changes in the decline rates at later times. SN 1994Y also demonstrat…
Johnson BVRI photometric data for individual components of binary systems have been provided by ten Brummelaar et al. (2000). This is essential because such binaries could play a critical role in calibrating the single-star stellar evolution theory. While they derived the effective temperature from their estimated spectral type, we infer metallicity-dependent Teffs from a minimizing method fitting the B-V, V-R and V-I colours. For this purpose, a grid of 621,600 flux distributions were computed from the Basel Stellar Library (BaSeL 2.2) of model-atmosphere spectra, and their theoretical colour…
We present multicolour broad band ($BVRI$) 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 f…
Photometric surveys of transNeptunian objects (TNOs) and Centaurs have suggested possible correlations between some orbital parameters and surface colors of classical objects, scattered disk objects (SDOs), and Centaurs. However, larger sample sizes are needed in order to corroborate or rule out the possible correlations and find some possible new ones. We use VLT-FORS images through BVRI filters of 32 Kuiper Belt Objects (KBOs) and obtain their colors after proper reduction and calibration. We study the possible correlations merging these new measurements with the VLT published results from t…
Calibrated Tully-Fisher relations ''absolute magnitude - HI line width'' for spiral galaxies oriented edge-on are derived from published data. The slope of the linear fits, especially in R- and I- bands, is close to the value of -10, as predicted by the theory. The standard errors of the relations in B, V, R and I bands are 0.40, 0.36, 0.31 and 0.34 mag, corresponding to relative distance errors of 18%, 17%, 14% and 16%, respectively. The magnitude of an edge-on galaxy appears to be a good distance indicator.
We present one of the results of $BVRI$ photometry of the hosts of GRB for the host galaxy of GRB 970508 and the theoretical modeling of its continuum spectral energy distribution (SED) to show that it is important to take into account internal extinction in the host galaxies. We compared the BVRI broad-band flux spectrum of the host to template SEDs of local starburst galaxies and found that there is a significant internal extintion in this host. Moreover, this comparison allows us to derive the absolute magnitude (M_{B_{rest}}) and rouhgly estimate reddening (A_V). Population synthesis model…
We present previously unpublished BVRI photometry of the Type Ia supernovae 1999cc and 2000cf along with revised photometry of SN 1999cl. We confirm that SN 1999cl is reddened by highly non-standard dust, with R_V = 1.55 +/- 0.08. Excepting two quasar-lensing galaxies whose low values of R_V are controversial, this is the only known object with a published value of R_V less than 2.0. SNe 1999cl and 2000cf have near-infrared absolute magnitudes at maximum in good agreement with other Type Ia SNe of mid-range decline rates.
We present B and V CCD aperture photometry for a morphologically-selected sample of forty-nine southern, extreme late-type spiral galaxies. All objects are moderate-to-low surface brightness Local Supercluster field galaxies that were detected previously in HI surveys. Our sample features objects that have optical luminosities, optical sizes, and HI masses which are at the low end for spiral galaxies. These objects are not a new class of galaxy, but are examples of a common type of spiral galaxy that has been under-represented in nearby galaxy samples. (Abridged).
Stars appearing in CCD images obtained over 224 nights during the course of 69 observing runs have been calibrated to the Johnson/Kron-Cousins BVRI photometric system defined by the equatorial standards of Landolt (1992, AJ, 104, 340). More than 15,000 stars suitable for use as photometric standards have been identified, where "suitable" means that the star has been observed five or more times during photometric conditions and has a standard error of the mean magnitude less than 0.02 mag in at least two of the four bandpasses, and shows no significant evidence of intrinsic variability. Many of…
R-band surface photometry is presented for 171 late-type dwarf and irregular galaxies. For a subsample of 46 galaxies B-band photometry is presented as well. We present surface brightness profiles as well as isophotal and photometric parameters including magnitudes, diameters and central surface brightnesses. Absolute photometry is accurate to 0.1 mag or better for 77% of the sample. For over 85% of the galaxies the radial surface brightness profiles are consistent with published data within the measured photometric uncertainty. For most of the galaxies in the sample HI data have been obtained…
We present UBVI surface photometry for 20.'5 X 20.'5 area of a late-type spiral galaxy NGC 300. In order to understand the morphological properties and luminosity distribution characteristics of NGC 300, we have derived isophotal maps, surface brightness profiles, ellipticity profiles, position angle profiles, and color profiles. By merging the I-band data of our surface brightness measurements with those of Boeker et al. (2002) based on Hubble Space Telescope observations, we have made combined I-band surface brightness profiles for the region of 0."02 < r < 500" and decomposed the profiles i…
We present photometrically calibrated images and surface photometry in the B, V, R, J, H, and K-bands of 25, and in the g, r, and K-bands of 5 nearby bright (Bo_T<12.5 mag) spiral galaxies with inclinations between 30-65 degrees spanning the Hubble Sequence from Sa to Scd. Data are from The Ohio State University Bright Spiral Galaxy Survey, the Two Micron All Sky Survey, and the Sloan Digital Sky Survey Second Data Release. Radial surface brightness profiles are extracted, and integrated magnitudes are measured from the profiles. Axis ratios, position angles, and scale lengths are measured fro…
A blue and variable optical counterpart of the X-ray transient XTE J0929-314 was identified on 2002 May 1. We conducted frequent BVRI broadband photometry on this object using the Mt Canopus 1-m telescope during May and June until it had faded to below 21'st magnitude. Nearly continuous I band CCD photometry on 2002 May 2, 3 and 4 revealed a ~ 10 % sinusoidal modulation at the binary period lasting ~ 6 cycles during the latter half of May 2. The phase indicates that the modulation may be due to a combination of emission by a hot spot on the disc and X-ray heating of the secondary. The emission…
BVRI CCD-based and near-IR (J) imaging, together with unfiltered photometry of the hot subdwarf B star PG 0856+121 are reported. Two close, faint, red, point-like sources are resolved. They account for the previously reported IR excess observed in this hot subdwarf. In addition, the new unfiltered differential photometry of PG 0856+121 confirms its previously reported pulsational nature. A comparison with the oscillation modes of stellar models suggests the possible presence of g modes.
We investigate recent claims that the Hubble sequence of spiral galaxies is scale-free. Fundamental to this investigation is the fact that within the photometric data of 86 spiral galaxies from de Jong & van der Kruit - from which these claims were made - a trend exists between morphological type and bulge profile shape. While late-type spiral bulges are described by an exponential luminosity profile, the early-type spiral bulges are better described by an r^{1/2} or r^{1/4} law. Taking the scale-lengths from the best-fitting surface brightness profile models (i.e. either using exponential, r^…
We have obtained deep surface photometry of the edge-on spiral galaxy NGC 4244. Our data reliably reach 27.5 R magnitude arcsec^{-2}, a significant improvement on our earlier deep CCD surface photometry of other galaxies. NGC 4244 is a nearby Scd galaxy whose total luminosity is approximately one magnitude fainter than the peak of the Sc luminosity function. We find that it has a simple structure: a single exponential disk, with a scale height h_Z = 246 +/- 2 pc, a scale length h_R = 1.84 +/- 0.02 kpc and a disk cutoff at a radius R(max) = 10.0 kpc (5.4 scale lengths). We confirm a strong cuto…
We present mass distributions obtained from near-infrared (NIR) surface brightness decompositions and rotation curve fitting of a sample of early-type spiral galaxies. Bulge and disk mass-to-light (M/L) ratios, dark halo parameters, and the modified Newtonian dynamics (MOND) acceleration parameter are derived. We find that the mean disk NIR M/L is higher than that of the bulge, and comparison with stellar population synthesis models implies that early-type spiral bulges are, on average, younger and more metal rich than disks. NIR disk M/L is found to depend on disk luminosity, consistently wit…
All slightly extended sources were identified on deep K-band maps of 46 spiral galaxies reaching at least K=20.3 mag/arcsec2 at a signal-to-noise level of 3. The galaxies had inclination angles <65 deg and linear resolutions <100 pc with seeing better than 1". The sample includes both barred and normal spirals with a wide spread in types. We also analyzed J- and H-band colors for 4 galaxies for which such images were available. An apparent magnitude limit of K = 19 mag was used for the sources analyzed in order to avoid marginal detections. Furthermore, we derived the source distributions of m…
The first results of an observational programme aimed at mapping a sample of face--on spiral galaxies in the NIR are presented. This paper shows the surface photometry of the first ten galaxies in the sample. The data were taken in the broad band $J$ (1.2 $μ$m) and $K_{s}$ (2.2 $μ$m) filters. The sources were selected mainly according to their size and brightness in order to suit the characteristics of the CAIN 2D NIR camera on the 1.5 m Carlos Sánchez Telescope (Tenerife, Spain). The primary scientific goal is to provide a comprehensive and uniform database of the main structural and photomet…
We present BVRI CCD surface photometry for the central (6'.35 X 6'.35) regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R < 225") and NGC 205 (R < 186") show excess components in the central regions. The colors of NGC 185 get bluer inward at R < 25", while they remain constant at R >= 25". The colors of NGC 205 get bluer inward at 1" < R < 50", and remain flat outside. Our photometry, supplemented by the photometry based on the far-ultraviolet and visual images of the HST archive data, shows that there is an inversion of c…
Relying on his photometry of galaxies, Holmberg (1958) found, more than 40 years ago, that the color indices of paired galaxies were closely correlated. Our deep broad-band BVRI CCD photometry of 45 (S+S) pairs from the Karachentsev (1972) catalogue (see Hernandez Toledo and Puerari, this volume), and additional (B-V) color information from the literature (50 extra (S+S) pairs), help us to confirm the effect. This "Holmberg Effect" has long been remained unverified and not explained yet.
We present BVRI photometry of the Type Ia supernovae 1999da, 1999dk, 1999gp, 2000bk, and 2000ce, plus infrared photometry of three of these. These objects exhibit the full range of decline rates of Type Ia supernovae. Combined optical and infrared data show that families of V - infrared color curves can be used to derive the host extinction (A_V) of these objects. Existing data do not yet allow us to construct these loci for all color indices and supernova decline rates, but the V-K color evolution is sufficiently uniform that it allows the determination of host extinction over a wide range of…
We perform a detailed photometric study of the stellar populations in a Galactic Field at l = 232, b = -6 in the Canis Major (CMa) constellation. We present the first U,B,V,I photometry of the old open cluster Auner1 and determine it to be 3.25 Gyr old and to lie at 8.9 kpc from the Sun. In the background of the cluster, at more than 9 kpc, we detect a young population most probably associated to the Norma Cygnus spiral arm. Furthermore, we detect the signature of an older population and identify its Turn Off and Red Giant Branch. This population is found to have a mean age of 7 Gyrs and a mea…
We present I-band photometry, long-slit optical spectroscopy, and new aperture synthesis HI observations for eight late-type spirals with rotation velocities in the range 243 km/s < V_{rot} < 308 km/s. The sample will be used to study the structure and angular momentum of disks at the high-mass end of the spiral galaxy population; here we discuss the basic properties of these ``fast rotators'', and derive hybrid optical/HI rotation curves for each. Despite the presence of HI warps and low-mass companions in many systems, their kinematics are regular and there is excellent agreement between opt…
We present optical and near-infrared (NIR) surface brightness and colour profiles,in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 degrees. We describe in detail the observations and the determination of colour parameters. Calibrated monochromatic and real-colour images are presented, as well as colour index maps. This data set, tailored for the study of the population characteristics of galaxy bulges, provides useful information on the colours of inner disks as well. In related papers, we have…
CCD BVRI photometry is presented for two type Ia supernovae 2000E and 2001V, for SN Ib 2001B and SN II-P 2001X. The parameters of light curves and absolute magnitudes at maximum light are estimated. It is shown that all four supernovae are typical for their classes considering the shape of their light curves and maximum luminosity.
In integrated-light, some color-color diagrams that use optical and near-infrared photometry show surprisingly orthogonal grids as age and metallicity are varied, and they are coming into common usage for estimating the average age and metallicity of spiral galaxies. In this paper we reconstruct these composite grids using simple stellar population models from several different groups convolved with some plausible functional forms of star formation histories at fixed metallicity. We find that the youngest populations present (t<2 Gyr) dominate the light, and because of their presence the age-m…
We present near-infrared, H-band (1.65 um), surface photometry of 174 spiral galaxies in the area of the Pisces-Perseus supercluster. The images, acquired with the ARNICA camera mounted on various telescopes, are used to derive radial profiles of surface brightness, ellipticities, and position angles, together with global parameters such as H-band magnitudes and diameters. The mean relation between H-band isophotal diameter D_{21.5} and the B-band D_{25} implies a B-H color of the outer disk bluer than 3.5; moreover, D_{21.5}/D_{25} depends on (global) color and absolute luminosity. The correl…
A new analysis of CCD-based BVRI broad-band photometry for the globular cluster NGC2419 is presented, based on 340 CCD images either donated by colleagues or retrieved from public archives. The calibrated results have been made available through my Web site. I compare the results of my analysis with those of an independent analysis of a subset of these data by Saha et al. (2005, PASP, 117, 37), who have found a color-dependent discrepancy of up to 0.05 mag between their I-band photometry and mine for stars in this cluster. I conclude that a major part of the discrepancy appears to be associate…
We exclude hydrogen burning stars, of any mass above the hydrogen-burning limit and any metallicity, as significant contributors to the massive halos deduced from rotation curves to dominate the outer parts of spiral galaxies. We present and analyse images of 4 nearly edge-on bulgeless spiral galaxies (UGC711, NGC2915, UGC12426, UGC1459) obtained with ISOCAM (The CAMera instrument on board the Infrared Space Observatory) at 14.5micron and 6.75micron. Our sensitivity limit for detection of any diffuse infrared emission associated with the dark halos in these galaxies is a few tens of microJy pe…
The intriguing nearly face-on southern ringed spiral galaxy NGC 4622, the first galaxy definitively shown to have leading spiral structure, is revisited in this paper with new images from the Hubble Space Telescope's WFPC2, together with ground-based optical and near-IR imaging, and a Fabry-Perot H-alpha velocity field. The data provide new information on the disk/bulge/halo mix, rotation curve, star formation in the galaxy, and the sense of winding of its prominent spiral arms. Previously, we suggested that the weaker, inner single arm most likely has the leading sense, based on a numerical s…
There is a clear scarcity of structural parameters for stellar thick discs, especially for spiral galaxies located in high-density regions, such as galaxy clusters and compact groups. We have modelled the thin and thick discs of 4 edge-on spirals located in Abell clusters: NGC 705, ESO243G49, ESO187G19, LCSBS0496P. Deep I band images of NGC 705 were taken from the HST archive, whereas the remaining images were obtained with the Southern Telescope for Astrophysical Research (SOAR) in Gunn r filter. They reached surface brightness levels of $μ_I \simeq 26.0$ mag arcsec$^{-2}$ and $μ_r \simeq 26.…
We present the analysis of morphological and photometric properties of a sample of isolated spirals with (18) and without (11) an active nucleus, based on near-infrared imaging in the J and K' bands. The aim of this analysis is to find the differential properties that could be directly connected with the phenomenon of nuclear activity. We stress the importance of using isolated objects for that purpose. Our study shows that both sets of galaxies are similar in their global properties: they define the same Kormendy relation, their disk components share the same properties, the bulge and disk sc…
We obtained new VLT/ISAAC H-band observations for five MACHO LMC source stars and adjacent LMC field regions. After combining our near-IR photometry with HST/PC BVRI optical photometry, we compared the MACHO objects to the adjacent field stars in a variety of color-magnitude and color-color diagrams. These diagnostic diagrams were chosen to be sensitive to our hypothesis that at least some of the MACHO lenses were foreground Galactic disk or thick disk M dwarfs. For the five lensed objects we studied, our hypothesis could be ruled out for main sequence lens masses >= 0.1 Mo for distances out t…
We present a structural analysis of nearby galaxies in spiral-spiral pairs in optical BVRI bands and compare with the structures of isolated spiral galaxies and galaxies in ongoing mergers. We use these comparisons to determine how galaxy structure changes during galaxy interactions and mergers. We analyze light concentration (C), asymmetry (A), and clumpiness (S) parameters, and use the projections of CAS parameter space to compare these samples. We find that the CAS parameters of paired galaxies are correlated with the projected separations of the pair. For the widest and closest pairs, the …
We compare two methods of distance determination to spiral galaxies using optical/near-infrared (NIR) observations, the (I-K) versus M_K colour - absolute magnitude (CM) relation and the I and K-band Tully-Fisher relation (TFR). Dust-free colours and NIR absolute magnitudes greatly enhance the usefulness of the NIR CM relation as a distance indicator for moderately to highly inclined_spiral_ galaxies_in the field_ (inclinations between ~ 80 and 90 deg); by avoiding contamination by dust the scatter in the CM relation is significantly reduced, compared to similar galaxy samples published previo…
We present near-infrared (NIR) surface photometry of a sample of 14 early-type spirals with observed rotation curves. In this first paper, we report the results of two-dimensional parametric and non-parametric decompositions to separate the bulge and disk components; the parametric bulge is modeled with a generalized exponential law of integer index n, and the disk with a simple exponential. We find that the derived bulge parameters, for a given galaxy, vary systematically with the bulge shape index n. The mean early-type bulge has a best-fit n = 2.6, and 80% of the sample has best n of 2 or 3…
As the first step to determine disk mass-to-light ratios for normal spiral galaxies, we present the results of an imaging survey for planetary nebulae (PNe) in six nearby, face-on systems: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), NGC 5068, and NGC 6946. Using Blanco/Mosaic II and WIYN/OPTIC, we identify 165, 153, 241, 150, 19, and 71 PN candidates, respectively, and use the Planetary Nebula Luminosity Function (PNLF) to obtain distances. For M74 and NGC 5068, our distances of 8.6 +/- 0.3 Mpc and 5.4 +0.2/-0.4 Mpc are the first reliable estimates to these objects; for IC 342 (3.5 …
We present infrared imaging data in the J and K' bands obtained for 18 active spiral galaxies, together with 11 non active galaxies taken as a control sample. All of them were chosen to satisfy well defined isolation criteria so that the observed properties are not related to gravitational interaction. For each object we give: the image in the K' band, the sharp-divided image (obtained by dividing the observed image by a filtered one), the difference image (obtained by subtracting a model to the observed one), the color J-K' image, the ellipticity and position angle profiles, the surface brigh…
CCD observations in V, I and H$_α$ for NGC 3389 are used to present photometry of 61 HII regions. Their $α$ and $δ$ positions, diameters and their absolute luminosities have been determined. The luminosity and size distribution functions of the HII regions in NGC 3389 are discussed.
We study the effects of dusty spiral arms on the photometric properties of disk galaxies using a series of 2D radiative transfer models, approximating the arms with axially symmetrical rings. We find that dusty arms, as well as dusty disks, have a significant influence on the aperture photometry and surface brightness profiles altering colors of model galaxies. We suggest that, in addition to the conventionally modeled diffuse absorbing layers or disks, the dusty arms should be taken into account in spiral galaxy extinction studies.
Based on 13 nights of observations of four fields in NGC 300, we have set up an extensive sequence of stars with accurate BVI photometry covering a relatively large (25 x 25 arcmin) region centered on this galaxy. This sequence of standard stars is very useful for calibrating the photometry of variable stars and other objects in NGC 300 and other galaxies obtained from wide field mosaic images. Our standard star list contains B, V and I measurements for 390 stars. The accuracy of the zero points in the V filter and B-V color is better than 0.02 mag, and about 0.03 mag for the V-I color. We fou…
BVRI data for the majority of the objects of the RC catalogue with steep spectra and $m_R<24^m$ are presented. These data have been used to estimate colour redshifts and the age of stellar systems of host galaxies. By way of example of distant radio galaxies it is shown that this approach gives an accuracy of redshift estimates close to that for field galaxies ($\sim20$ %). The age estimates are less confident, however, the lower age limit for not too distant ($z<1.5$) objects is determined quite reliably. Several galaxies have been detected that have an age above that of the Universe at the g…
We explore the rich globular cluster (GC) system of the nearby Sa galaxy M104, the "Sombrero" (NGC 4594), using archive WFPC2 data. The GC colour distribution is found to be bimodal at the > 99% level, with peaks at V-I = 0.96+/-0.03 and 1.21+/-0.03 (corrected for foreground reddening). The inferred metallicities are very similar to those of globular clusters in our Galaxy and M31. However the Sombrero reveals a much enhanced number of red (metal-rich) GCs compared to other well-studied spirals. Because the Sombrero is dominated by a huge bulge and only has a modest disk, we associate the two …
We present results of broad band {BVRI} observations of a sample of galaxies with a low surface brightness (LSB) disk and a bulge. These galaxies are well described as exponential disks and exponential bulges with no preferred value for either scale length or central surface brightness. The median {B} band disk scale length is 12.6 kpc (H_(0) = 75 km s^{-1} Mpc^{-1}) which is much larger than scale lengths of typical (disk dominated) LSB or high surface brightness (HSB) galaxies. Furthermore, the disk and bulge scale lengths are correlated, suggesting a coupling in the formation. Bulge dominat…
Narrow-band H-alpha+[NII] and broadband R images and surface photometry are presented for a sample of 29 bright (M_B < -18) isolated S0-Scd galaxies within a distance of 48 Mpc. These galaxies are among the most isolated nearby spiral galaxies of their Hubble classifications as determined from the Nearby Galaxies Catalog (Tully 1987a).
As a result of an extensive observational campaign targeting the Virgo cluster, we obtained integrated (drift-scan mode) optical spectra and multiwavelength (UV,U,B,V,H) photometry for 124 and 330 galaxies, respectively, spanning the whole Hubble sequence, and with m_p<=16 (M_p<=-15). These data were combined to obtain galaxy SEDs extending from 2000 to 22000 A. By fitting these SEDs with synthetic ones derived using Bruzual & Charlot population synthesis models we try to constrain observationally the SFH of these galaxies. Assuming a Salpeter IMF and an analytical form for the SFH, the fit fr…
A new method of evaluating relative (arm with respect to the interarm disk) star formation rates and relative star formation efficiencies, together with spiral arm-amplitudes, as a function of the galactocentric radius, using broad-band photometry is derived. The classical method for obtaining star formation rates from H_alpha photometry is discussed, and a new method is derived for diagnosing the possible presence of biased star formation due to different initial mass functions in the arms and in the interarm disk. As an example, these methods are applied to the spiral galaxies NGC 4321 and N…
We present the rest-frame B-band Tully-Fisher relation for a sample of 8 cluster spiral galaxies at z = 0.83 and 19 field spirals at z = 0.15-0.90 based on VLT spectroscopy and HST photometry. No strong difference is detected between the cluster and the field galaxies, but we find some evidence that the cluster spirals are ~0.5-1 mag brighter than the field ones at a fixed rotation velocity. Although only a ~1.5-2 sigma result, if confirmed with larger samples this effect could be due to the cluster spirals experiencing a period of enhanced star formation while falling into the cluster.
We introduce a dataset of 142 mostly late-type spiral, irregular, and peculiar (interacting or merging) nearby galaxies observed in UBVR at the Vatican Advanced Technology Telescope (VATT), and present an analysis of their radial color gradients. We confirm that nearby elliptical and early- to mid-type spiral galaxies show either no or only small color gradients, becoming slightly bluer with radius. In contrast, we find that late-type spiral, irregular, peculiar, and merging galaxies become on average redder with increasing distance from the center. The scatter in radial color gradient trends …
We have collected a large body of NIR (H band), UV (2000 A) and Halpha measurements of late-type galaxies. These are used, jointly with spectral evolutionary synthesis models, to study the initial mass function (IMF) in the mass range m > 2 Mo. For spirals (Sa-Sd), Magellanic irregulars (Im) and blue compact dwarfs (BCD), our determination is consistent with a Salpeter IMF with an upper mass cutoff M_up = 80 Mo. The history of star formation and the amount of total gas (per unit mass) of galaxies are found to depend primarily on their total masses (as traced by the H band luminosities) and onl…
We have used a large sample of low-inclination spiral galaxies with radially-resolved optical and near-infrared photometry to investigate trends in star formation history with radius as a function of galaxy structural parameters. A maximum likelihood method was used to match all the available photometry of our sample to the colours predicted by stellar population synthesis models. The use of simplistic star formation histories, uncertainties in the stellar population models and regarding the importance of dust all compromise the absolute ages and metallicities derived in this work, however our…
