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HI content in galaxies in loose groups
Gas deficiency in cluster spirals is well known and ram-pressurestripping is considered the main gas removal mechanism. In some compactgroups too gas deficiency is reported. However, gas deficiency in loosegroups is not yet well established. Lower dispersion of the membervelocities and the lower density of the intragroup medium in small loosegroups favour tidal stripping as the main gas removal process in them.Recent releases of data from the HI Parkes All-Sky Survey (HIPASS) andcatalogues of nearby loose groups with associated diffuse X-ray emissionhave allowed us to test this notion. In this paper, we address thefollowing questions: (i) do galaxies in groups with diffuse X-rayemission statistically have lower gas content compared to the ones ingroups without diffuse X-ray emission? (ii) does HI deficiency vary withthe X-ray luminosity, LX, of the loose group in a systematicway? We find that (i) galaxies in groups with diffuse X-ray emission, onaverage, are HI deficient, and have lost more gas compared to those ingroups without X-ray emission; the latter are found not to havesignificant HI deficiency; (ii) no systematic dependence of the HIdeficiency with LX is found. Ram-pressure-assisted tidalstripping and evaporation by thermal conduction are the two possiblemechanisms to account for this excess gas loss.
| The SCUBA Local Universe Galaxy Survey - III. Dust along the Hubble sequence
We present new results from the Submillimetre Common-User BolometerArray (SCUBA) Local Universe Galaxy Survey (SLUGS), the first largesystematic submillimetre (submm) survey of the local Universe. Since ourinitial survey of a sample of 104 IRAS-selected galaxies we have nowcompleted a survey of a sample of 81 optically selected galaxies,observed with the SCUBA camera on the James Clerk Maxwell Telescope.Since SCUBA is sensitive to the 90 per cent of dust too cold to radiatesignificantly in the IRAS bands our new sample represents the firstunbiased SCUBA survey of dust in galaxies along the whole length of theHubble sequence.We find little change in the properties of dust in galaxies along theHubble sequence, except a marginally significant trend for early-typegalaxies to be less-luminous submm sources than late types. Wenevertheless detected six out of 11 elliptical galaxies, although someof the emission may possibly be synchrotron rather than dust emission.As in our earlier work on IRAS galaxies we find that the IRAS and submmfluxes are well fitted by a two-component dust model with dustemissivity index β= 2. The major difference from our earlier workis that we find the ratio of the mass of cold dust to the mass of warmdust is much higher for our optically selected galaxies and can reachvalues of ~1000. Comparison of the results for the IRAS and opticallyselected samples shows that there is a population of galaxies containinga large proportion of cold dust that is unrepresented in the IRASsample.We derive local submm luminosity and dust mass functions, both directlyfrom our optically selected SLUGS sample, and by extrapolation from theIRAS Point Source Catalogue Redshift Survey (PSCz) survey using themethod of Serjeant and Harrison (by extrapolating the spectral energydistributions of the IRAS PSCz survey galaxies out to 850μm we probea wider range of luminosities than probed directly by the SLUGSsamples), and find excellent agreement between the two. We find them tobe well fitted by Schechter functions except at the highestluminosities. We find that as a consequence of the omission of coldgalaxies from the IRAS sample the luminosity function presented in ourearlier work is too low by a factor of 2, reducing the amount of cosmicevolution required between the low-z and high-z Universe.
| A search for Low Surface Brightness galaxies in the near-infrared. I. Selection of the sample
A sample of about 3800 Low Surface Brightness (LSB) galaxies wasselected using the all-sky near-infrared (J, H and Ks-band)2MASS survey. The selected objects have a mean central surfacebrightness within a 5'' radius around their centre fainter than 18 magarcsec-2 in the Ks band, making them the lowestsurface brightness galaxies detected by 2MASS. A description is given ofthe relevant properties of the 2MASS survey and the LSB galaxy selectionprocedure, as well as of basic photometric properties of the selectedobjects. The latter properties are compared to those of other samples ofgalaxies, of both LSBs and ``classical'' high surface brightness (HSB)objects, which were selected in the optical. The 2MASS LSBs have aBT_c-KT colour which is on average 0.9 mag bluerthan that of HSBs from the NGC. The 2MASS sample does not appear tocontain a significant population of red objects.All tables and Figs. 2a-c are only available in electronic form athttp://www.edpsciences.org
| A new catalogue of ISM content of normal galaxies
We have compiled a catalogue of the gas content for a sample of 1916galaxies, considered to be a fair representation of ``normality''. Thedefinition of a ``normal'' galaxy adopted in this work implies that wehave purposely excluded from the catalogue galaxies having distortedmorphology (such as interaction bridges, tails or lopsidedness) and/orany signature of peculiar kinematics (such as polar rings,counterrotating disks or other decoupled components). In contrast, wehave included systems hosting active galactic nuclei (AGN) in thecatalogue. This catalogue revises previous compendia on the ISM contentof galaxies published by \citet{bregman} and \citet{casoli}, andcompiles data available in the literature from several small samples ofgalaxies. Masses for warm dust, atomic and molecular gas, as well asX-ray luminosities have been converted to a uniform distance scale takenfrom the Catalogue of Principal Galaxies (PGC). We have used twodifferent normalization factors to explore the variation of the gascontent along the Hubble sequence: the blue luminosity (LB)and the square of linear diameter (D225). Ourcatalogue significantly improves the statistics of previous referencecatalogues and can be used in future studies to define a template ISMcontent for ``normal'' galaxies along the Hubble sequence. The cataloguecan be accessed on-line and is also available at the Centre desDonnées Stellaires (CDS).The catalogue is available in electronic form athttp://dipastro.pd.astro.it/galletta/ismcat and at the CDS via anonymousftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/5
| Extended dust emission in NGC 7465
We present SCUBA 850-μm, JCMT CO(J =2->1), B -band imaging and VLAHi observations of the NGC 7465/4/3 group of galaxies. The 850-μmemission associated with NGC 7465 extends to at least ~2R 25and is well correlated with the Hi. We investigate a range of possiblemechanisms by which dust beyond R 25 may be heated to givethe observed extended submillimetre emission. By modelling the dustheating by stars in two extreme geometries, we fail to find anyreasonable star formation scenario that is consistent with both the850-μm and optical data. Furthermore, we do not detect any CO(J=2->1) emission coincident with the extended dust and atomic gas aswould be expected if significant star formation were occurring. We showthat shock-heating of dust via cloud-cloud collisions in the strippedinterstellar medium of NGC 7465 could be sufficient to explain theextended 850-μm emission and lack of optical emission in the strippedgas, and suggest that cloud-cloud collisions may be an important dustheating mechanism in gas-rich systems.
| Near-Infrared photometry in J, H and Kn bands for polar ring galaxies. II. Global properties
We discuss the properties of the host galaxy and ring lightdistributions in the optical and near infrared bands for a sample ofPolar Ring Galaxies (PRGs), presented in Paper I (Iodice et al.\cite{paperI}). The goal of this work is to test different formationscenarios for PRGs, proposed by different authors in the last decades,by comparing their predictions with these new data. The strategy istwofold: i) the integrated colors of the main components in thesesystems are compared with those of standard morphological galaxy types,to investigate whether differences in colors are caused by dustabsorption or difference in stellar populations. We then derived anestimate of the stellar population ages in PRGs, which can be used toset constrains on the dynamical modeling and the time evolution of thesesystems; ii) we analyse the structural parameters of the host galaxy inorder to understand whether this component is a standard early-typesystem as its morphology suggests, and the light distribution in thepolar ring to measure its radial extension. These observational resultsindicate that the global properties of PRGs are better explained bydissipative merging of disks with un-equal masses as proposed by Bekki(1998), rather than the accretion-or stripping-of gas by a pre-existingearly-type galaxy.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Neutral Hydrogen and Dark Matter in Spiral Galaxies
The first part presents a brief review of the main HI properties ofisolated, normal spiral galaxies and of the phenomena which seem tocharacterize and dominate their internal metabolism. In the second partattention is drawn to all those processes, such as tidal interactions,accretion and mergers, that depend on the galaxy environment and mayplay a significant role in galaxy formation and evolution. In the thirdpart the observational evidence for the dark matter component of spiralgalaxies is discussed.
| Disk Galaxies in the Outer Local Supercluster: Optical CCD Surface Photometry and Distribution of Galaxy Disk Parameters
We report new B-band CCD surface photometry on a sample of 76 diskgalaxies brighter than B_T = 14.5 mag in the Uppsala General Catalogueof Galaxies that are confined within a volume located in the outer partof the Local Supercluster. With our earlier published I-band CCD andhigh signal-to-noise ratio 21 cm H I data, this paper completes ouroptical surface photometry campaign on this galaxy sample. As anapplication of this data set, the B-band photometry is used here toillustrate two selection effects that have been somewhat overlooked inthe literature but that may be important in deriving the distributionfunction of disk central surface brightness (CSB) of disk galaxies froma diameter- and/or flux-limited sample: a Malmquist-type bias againstdisk galaxies with small disk scale lengths (DSLs) at a given CSB and adisk inclination-dependent selection effect that may, for example, biastoward inclined disks near the threshold of a diameter-limited selectionif disks are not completely opaque in the optical. Taking intoconsideration these selection effects, we present a method ofconstructing a volume-sampling function and a way to interpret thederived distribution function of CSB and DSL. Application of this methodto our galaxy sample implies that if galaxy disks are optically thin,CSB and DSL may well be correlated in the sense that, up to aninclination-corrected limiting CSB of about 24.5 mag arcsec^-2 that isadequately probed by our galaxy sample, the DSL distribution of galaxieswith a lower CSB may have a longer tail toward large values unless thedistribution of disk galaxies as a function of CSB rises rapidly towardfaint values.
| Groups of galaxies. III. Some empirical characteristics.
Not Available
| Catalogue of HI maps of galaxies. I.
A catalogue is presented of galaxies having large-scale observations inthe HI line. This catalogue collects from the literature the informationthat characterizes the observations in the 21-cm line and the way thatthese data were presented by means of maps, graphics and tables, forshowing the distribution and kinematics of the gas. It containsfurthermore a measure of the HI extension that is detected at the levelof the maximum sensitivity reached in the observations. This catalogueis intended as a guide for references on the HI maps published in theliterature from 1953 to 1995 and is the basis for the analysis of thedata presented in Paper II. The catalogue is only available inelectronic form at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Total magnitude, radius, colour indices, colour gradients and photometric type of galaxies
We present a catalogue of aperture photometry of galaxies, in UBVRI,assembled from three different origins: (i) an update of the catalogueof Buta et al. (1995) (ii) published photometric profiles and (iii)aperture photometry performed on CCD images. We explored different setsof growth curves to fit these data: (i) The Sersic law, (ii) The net ofgrowth curves used for the preparation of the RC3 and (iii) A linearinterpolation between the de Vaucouleurs (r(1/4) ) and exponential laws.Finally we adopted the latter solution. Fitting these growth curves, wederive (1) the total magnitude, (2) the effective radius, (3) the colourindices and (4) gradients and (5) the photometric type of 5169 galaxies.The photometric type is defined to statistically match the revisedmorphologic type and parametrizes the shape of the growth curve. It iscoded from -9, for very concentrated galaxies, to +10, for diffusegalaxies. Based in part on observations collected at the Haute-ProvenceObservatory.
| Global structure and formation of polar-ring galaxies.
We present an analysis of structural features of all known galaxies withoptical polar rings. We find a clear dichotomy for objects of thispeculiar class. Bulge-dominated S0 galaxies possess only short narrowrings, while disk-dominated objects always have wide extended polarrings. We try by gas dynamical simulations to explain such a segregationby dependence of the ring-forming process on different galaxypotentials. It is found that the total mass captured into the ringduring an encounter of a host-ring system with a gas-rich spiral galaxyof comparable mass exceeds 10^9^Msun_ (or about 10% of allgas in the donor galaxy), which is of the order of that found byobservation. The process of gas to gather into a steady-state ring takesapproximately (7-9)x10^8^years. This time is somewhat shorter for ringsforming around bulge-dominated galaxies. We also present observationalarguments for S0 galaxies with extended rings to be similar to late-typespirals by their photometric properties, while numerical modelling ofthe extended ring formation suggests that these galaxies must possessmassive dark halos as well. In this case, the sizes of the modelledrings turn out large enough (up to 30kpc in diameter), and the timescale for ring formation is prolonged up to several Gyrs.
| Neutral hydrogen observations of elliptical galaxies. II. The IRAS sample.
HI observations are reported for a total of 53 IRAS elliptical galaxies.Nearby confusing sources may be responsible for some of the 33detections. There are 24 isolated detected galaxies, which can be splitinto two groups, one having the same M_HI_/L_B_ ratio as the ellipticalgalaxies from the RSA (M_HI_/L_B_=0.030+/-0.026). A second group is morethan six times richer in HI (M_HI_/L_B_=0.206+/-0.105). The "HI-rich"galaxies have blue colors like spiral galaxies and have a tendencytowards higher average dust temperatures. The large number of ellipticalgalaxies in compact groups (in this sample) suggests that gravitationalinteractions and mergers may be an important source of interstellarmatter for elliptical galaxies.
| The molecular cloud content of early-type galaxies. V. CO in elliptical galaxies.
A survey of CO emission in 29 far-IR selected elliptical galaxiesresulted in 16 detections, of which 3 remain tentative. The moleculargas masses range from 2x10^6^Msun_ to1x10^9^Msun_, and appear to be unrelated to the underlyingstellar population. This suggests an external origin of the gas. Most ofthe elliptical galaxies with a molecular gas component have agas-to-dust mass ratio of ~700, where dust masses are derived from theIRAS fluxes, but some appear to have a ratio as low as 50. A smallapparent gas-to-dust mass ratio is also found for some late-typegalaxies, and is correlated with a low dust temperature. We suggest thata large part of the far-infrared emission from these galaxies (bothearly- and late-types) comes from dust associated with the atomic gascomponent rather than star forming regions associated with the moleculargas, and that they contain a cold dust component. Low excitationtemperatures for CO transitions in galaxies with cold dust could lead toan underestimate of the molecular gas mass by a factor of 5. The averageM_H_2__/M_HI_ ratio for the elliptical galaxies is 2-5 times lower thanfor normal spiral galaxies. Field ellipticals appear more likely tocontain an observable molecular gas component than those ellipticalsresiding in groups and clusters.
| Neutral hydrogen distribution in the NGC 7465 group of galaxies
High resolution neutral hydrogen observations in the NGC 7465 smallgroup of galaxies reveal tidally distorted H I morphology and kinematicsin four out of the five members studied. An H I 'bridge' was detectedconnecting, in projection, UGC 12313 and NGC 7463 or the subgroup as awhole. The sides of both galaxies connected with the bridge show signsof recent interaction. The bridge has a small velocity gradient and itsradial velocities merge with those of the southeast part of UGC 12313,suggesting a physical link between the two. The H I emission from NGC7463 is well separated in velocity space from that of NGC 7464/7465 andshows peculiar morphology and kinematics as a result of 'high-velocity'gas occurring above the eastern side of the disk. An r approximatelyequals 80 sec ring around NGC 7465 dominates the H I emission from NGC7464/7465. There is evidence to suggest that it represents a polar ringaround NGC 7465 and could be pulled out from NGC 7464 during a closeencounter with NGC 7465. UGC 12321 is the only galaxy which showsoverall unperturbed morphology and its H I kinematics are consistentwith a disk galaxy seen nearly edge-on. Nevertheless, we identified twoasymmetries in its H I distribution.
| Spectrographic study of a large sample of KISO ultraviolet excess galaxies. I. The data
We present the results of a medium-resolution spectroscopic study of 142Kiso ultraviolet-excess galaxies (KUGs), mostly of "compact","irregular" and "interactive pair" morphological types in the Kisocatalog. 137 objects are found to exhibit at least one emission line.The astrophysical implications of this survey will be discussed in acompanion paper (Comte et al. 1994).
| Far-Infrared Mapping of Dusty Elliptical Galaxies
The initial results from a program to map the thermal far-infraredemission from dusty elliptical galaxies are presented. Using the Yerkes60-Channel Far-Infrared Camera on the Kuiper Airborne Observatory wehave imaged three elliptical galaxies at 160mu with a resolution of44('') (NGC 5666, NGC 6524, and the interacting system NGC 7463/4/5) andone at 100mu with a resolution of 25('') (NGC 6524). Observations of NGC1275 (Per A) are scheduled for December 1993 and may also be discussed.The E/S0 system NGC 6524 is dominated by a central point source at both100 and 160mu with a dust temperature of 29(deg) K, in agreement withIRAS data and recent submillimeter observations of the central regionsfrom the James Clark Maxwell Telescope on Mauna Kea. In addition, NGC6524 shows low-level extended dust emission at 160mu which is notdetected at 100mu . The temperature of this dust is apparently less than20(deg) K. Preliminary results from JCMT submillimeter observations ofother dusty ellipticals may also be presented. This research wassupported by NASA grant NGR 14-001-227 to the University of Chicago.
| H I 21 centimeter observations and I-band CCD surface photometry of spiral galaxies behind the Virgo Cluster and toward its antipode
Sample selection, radio and optical data acquisition and reduction, andobservation results are presented for spiral galaxies behind the VirgoCluster and toward its antipode. I-band CCD photometry was obtained forall the bright galaxies and part of the sample of faint galaxies in thetwo local volumes was studied. The statistical properties of the galaxysamples are discussed.
| A revised catalog of CfA1 galaxy groups in the Virgo/Great Attractor flow field
A new identification of groups and clusters in the CfA1 Catalog ofHuchra et al. is presented, using a percolation algorithm to identifydensity enhancements. It is shown that in the resulting catalog,contamination by interlopers is significantly reduced. The Schechterluminosity function is redetermined, including the Malmquist bias.
| Millimeter and submillimeter continuum emission from early-type galaxies
Twenty-two early-type galaxies that were detected by IRAS have beensearched for continuum emission at millimeter and submillimeterwavelengths using the James Clerk Maxwell Telescope (JCMT). IRAS wasrelatively insensitive to cold dust that emits primarily at these longerwavelengths. In this first survey we were able to detect or achieveuseful limits on the emission from 14 of the 22 galaxies observed. Fromthese data we estimate upper limits on the dust temperature and lowerlimits on the mass of dust within the JCMT beam. These results arecompared with H I and CO data and with the blue luminosities of thegalaxies. The results are consistent with a model where the dust-to-gasratio is similar to the Galactic one, and the amount of cold dust is anorder of magnitude greater than the amount of warm dust (as is also seenin our Galaxy). The total dust mass, normalized to the luminosity of theentire galaxy, is much lower than is found in spiral galaxies, asexpected.
| A survey of the Pisces-Perseus supercluster. VI - The declination zone +15.5 deg to 21.5 deg
New results are presented of Arecibo observations in the 21 cm line of765 galaxies with declinations between 15.5 deg and 21.5 deg, in thePisces-Perseus supercluster zone. If considered independently on theneighboring parts of sky, this region, to the South of the superclusterridge, shows significantly less evidence of structure on large scales inexcess of 30 Mpc, contrasting substantially with the characteristics ofthe declination zones immediately to the North.
| Optical positions and 327 MHz flux-densities of UGC galaxies in selected Westerbork fields
The study presents accurate optical positions of 421 UGC galaxies whichare used to search for 30 92-cm WSRT fields observed for emission fromthese galaxies. Good 92-cm flux densities were obtained for 140galaxies, marginal flux densities for 71 galaxies, and upper limits for210 galaxies. For 35 galaxies, spectral indices in the decimeterwavelength range are determined. The mean spectral index for spiralgalaxies (0.72 +/- 0.03) is very similar to that of elliptical galaxies(0.64 +/- 0.10). The four multiple systems in the sample have a muchflatter spectral index (-0.21 +/- 0.07), from which the presence of asignificant thermal component in their total radio emission issuggested. Comparison with IRAS results show that about half of thegalaxies detected at radio wavelengths are detected in the FIR. It isproposed that some spiral galaxies are anomalously weak in the IR ascompared with their radio brightness.
| General study of group membership. II - Determination of nearby groups
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
| A study of the NGC 7448 group of galaxies
Optical CCD images and spectra, 21-cm H I line observations, and radiocontinuum and FIR maps of six members of the NGC 7448 group of galaxieswere studied: NGC 7448, the compact NGC 7463/64/65 subgroup, UGC 12313,and UGC 12321. No clear evidence of ongoing catalcysmic interactionsbetween the group members was found, although the presence of themerger-type galaxies NGC 7464 and 7465 indicates that such events didtake place in the more distant past. Signs of recent interactions of aless violent nature are also seen.
| Molecular gas in elliptical galaxies
C-12O(2-1) observations of 24 FIR-bright ellipticals, as well as fiveother early-type galaxies, including one FIR-faint elliptical, IC 2006,are reported. The detected ellipticals are found to have typicalmolecular gas masses of about 10 to the 7th - 10 to the 8th solarmasses, similar to their H I masses, and an approximately power-lawdistribution of M(H2)/L(B), extending to much lower values than for thespirals. The lenticular galaxies have CO properties intermediate betweenthe elliptical and spiral systems. It is concluded that theseellipticals have global interstellar medium properties similar to thosein late-type galaxies, but on a much smaller scale. A comparison of theproperties of those ellipticals which have been detected in CO with theundetected galaxies indicates that the molecular gas may occurpreferentially in the bluer, lower luminosity dwarf ellipticals, whichhave more than twice the detection rate of the brighter galaxies.
| Detection of CO emission in the elliptical galaxies NGC 3265 and NGC 5666
From observations of seven elliptical galaxies selected by the strengthof their far-infrared (FIR) fluxes, the detection of CO (2 - 1) in thecentral regions of NGC 3265 and NGC 5666, classified as E4 and Ec,respectively, is reported. Observed with the FWHM beam of 17 arcsec ofthe IRAM telescope, the CO radial velocities and line widths agree wellwith H I spectra emitted from a much more extended region, caused partlyby rigid rotation in their nuclear regions but also implying acontribution from extensive noncircular motions in the interstellar gas.The shapes of the CO profiles indicate velocity structure within thebeam. The observational ratios of CO/H I fluxes are similar to thosefound in early-type galaxies. The data also imply H2 masses of 1.7 x 10to the 8th and 3.8 x 10 to the 8th solar masses for the central regionsof NGC 3265 and NGC 5666, respectively, giving for those regions H2/H Imass ratios of about three that are comparable to what is observed forthe inner region of the Milky Way.
| Associations between quasi-stellar objects and galaxies
A table is presented here listing all close pairs of QSOs and galaxiesthat were found in a computer-aided search of catalogs of QSOs andbright galaxies and an extensive search of the literature. There is alarge excess of pairs with separations of 2 arcmin lor less, or about 60kpc, over the numbers expected if the configurations were accidental.The angular separation for 392 pairs adds to the evidence for physicalassociation, and it is shown that selection effects are not important. Ageneral rule is stated that QSOs tend to lie in the vicinity of normalgalaxies much more often than is expected by chance whether or not thegalaxies and the QSOs have the same redshifts. It is emphasized thatthis rule cannot be explained in terms of gravitational microlensing,and it is concluded that some part of the redshift of all classes ofactive nuclei is not associated with the expansion of the universe.
| Observations of galaxies in groups at 102 MHz
Observations of 325 galaxies in groups were carried out at a frequencyof 102 MHz via the scintillation method. Radio emission was found in 42of these components. Eleven of these have a meridional component.
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