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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 Supernova Rate-Velocity Dispersion Relation in the Interstellar Medium
We investigate the relationship between the velocity dispersion of thegas and the supernova (SN) rate and feedback efficiency withthree-dimensional numerical simulations of SN-driven turbulence in theinterstellar medium (ISM). Our simulations aim to explore the constancyof the velocity dispersion profiles in the outer parts of galactic disksat ~6-8 km s-1 and the transition to the starburst regime,i.e., high star formation rates (SFRs) associated with high velocitydispersions. With our fiducial value of the SN feedback efficiency(i.e., ε=0.25, corresponding to an injected energy per SN of0.25×1051 ergs), our results show that (1) SN drivingleads to constant velocity dispersions of σ~6 km s-1for the total gas and σHI~3 km s-1 for the HI gas, independent of the SN rate, for values of the rate between 0.01and 0.5 the Galactic value (ηG) (2) the position of thetransition to the starburst regime (i.e., location of sharp increase inthe velocity dispersion) at around SFR/area~=5×10-3 to10-2 Msolar yr-1 kpc-2observed in the simulations is in good agreement with the transition tothe starburst regime in the observations (e.g., NGC 628 and NGC 6949);(3) for the high SN rates, no H I gas is present in the simulations box;however, for the total gas velocity dispersion, there is good agreementbetween the models and the observations; (4) at the intermediate SNrates (η/ηG~0.5-1), taking into account the thermalbroadening of the H I line helps reach a good agreement in that regimebetween the models and the observations; and (5) forη/ηG<0.5, σ and σHI fallbelow the observed values by a factor of ~2. However, a set ofsimulations with different values of ɛ indicates that, forlarger values of the SN feedback efficiencies, velocity dispersions ofthe H I gas of the order of 5-6 km s-1 can be obtained, incloser agreement with the observations. The fact that forη/ηG<0.5, the H I gas velocity dispersions are afactor of ~2 smaller than the observed values could result from the factthat we might have underestimated the SN feedback efficiency. On theother hand, it might also be an indication that other physical processescouple to the stellar feedback in order to produce the observed level ofturbulence in galactic disks.
| Supernova 2004fu in NGC 6949
IAUC 8436 available at Central Bureau for Astronomical Telegrams.
| Supernova 2004fu in NGC 6949
IAUC 8428 available at Central Bureau for Astronomical Telegrams.
| The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
| 1WGA J1216.9+3743: Chandra Finds an Extremely Steep Ultraluminous X-Ray Source
We report the discovery of a new ultraluminous X-ray source (ULX) in thenearby galaxy NGC 4244 from Chandra archival data. The source, 1WGAJ1216.9+3743, is one of the least luminous and softest ULXs discoveredso far. Its X-ray spectrum is the best available for a representative ofthe soft ULXs, a class of sources recently discovered by Chandra andXMM-Newton. 1WGA J1216.9+3743 appears pointlike in the Chandra image andhas a complex spectral shape; a multicolor disk model, suitable forbrighter ULXs, is inadequate for this source. The 1WGA J1216.9+3743spectrum is heavily absorbed (NH~1-4×1021cm-2) and very soft. The best-fit power-law model givesΓ~5 and implies a luminosityL(0.5-10keV)~1039 ergs s-1. Acomparison with previous detections shows that, despite the variabilitydisplayed by the source during the Chandra observation, the 1WGAJ1216.9+3743 count rate, spectral shape, and absorption are practicallyunchanged over a 9 yr period. We also performed deep optical imaging ofthe field containing the X-ray source and found a possible R~23.7counterpart.
| 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.
| The ROSAT/IRAS Galaxy Sample Revisited
Galaxies in the ROSAT/IRAS sample were selected by their soft X-ray(0.1-2.4 keV) and far-infrared (lambda = 60 μm) emission. Therelatively large uncertainties in the original ROSAT and IRAS positionscaused some contamination by close pairs and forced the exclusion ofmost ``high-flux'' (S > 10 Jy at lambda = 100 μm) IRAS sourcesfrom the original sample. We used new 1.4 GHz VLA images of all objectsnorth of delta = -45 deg along with improved X-ray and far-infraredpositions to eliminate incorrect identifications, many of which appearedto be starburst galaxies with high X-ray luminosities, log [X(ergs^-1)]> 43. We also used VLA images to search for new X-ray identificationsamong the ``high-flux'' sources with delta > -45 deg. Only two werefound, indicating that luminous starburst galaxies have relatively lowsoft X-ray luminosities, in part due to absorption by a denseinterstellar medium. No starburst galaxies in our revised sample haveX-ray luminosities approaching log [X(ergs^-1)] = 43. We conclude thatmost galaxies in the revised ROSAT/IRAS sample contain X-ray-emittingactive galactic nuclei (AGNs) residing in star-forming disks that emitmost of the lambda = 60 μm radiation. Normal and starburst galaxiesprobably do not account for a significant fraction of the soft X-raybackground.
| Kinematics of the local universe. VII. New 21-cm line measurements of 2112 galaxies
This paper presents 2112 new 21-cm neutral hydrogen line measurementscarried out with the meridian transit Nan\c cay radiotelescope. Amongthese data we give also 213 new radial velocities which complement thoselisted in three previous papers of this series. These new measurements,together with the HI data collected in LEDA, put to 6 700 the number ofgalaxies with 21-cm line width, radial velocity, and apparent diameterin the so-called KLUN sample. Figure 5 and Appendices A and B forcorresponding comments are available in electronic form at thehttp://www.edpsciences.com
| Search and Redshift Survey for IRAS Galaxies behind the Milky Way and Structure of the Local Void
This is the third and final paper of our systematic visual search forIRAS galaxies behind the Milky Way at |b| <= 15 deg. This paperpresents a catalog of 950 IRAS galaxies with 60 mu m flux densitieslarger than 0.6 Jy located between l = 0 deg and 150 deg, of which 293are newly identified by this search. We made a redshift survey for theidentified galaxies and obtained new redshift data of 171 galaxies. Wealso present newly measured redshifts of 27 IRAS galaxies between l =150 deg and 225 deg at |b| <= 15 deg. In this paper we studied thestructure of the Local void using IRAS galaxies and galaxies from theThird Reference Catalogue of Bright Galaxies in the region l = 30deg--120 deg and b = -50 deg to +30 deg. The center of the Local voidturned out to be located at l ~ 60 deg, b ~ -15 deg, and cz ~ 2500 kms-1, and the size is about 2500 km s-1 along the direction toward thecenter.
| Classification of IRAS-selected X-Ray Galaxies in the ROSAT All-Sky Survey
To explore the possibility that star-forming galaxies or obscuredSeyfert galaxies, both of which are known to be luminous infraredsources, contribute significantly to the cosmic X-ray background, wehave carried out an extensive program to obtain accurate spectroscopicclassifications of the BoIler et al. (1992) catalog of IRAS sourcesdetected in the ROSAT All-Sky Survey. This has involved careful opticalspectroscopy, a review of the literature, and efforts to reveal thecontaminants in the sample. Classifications have been determined for 210of the 241 X-ray sources in the catalog; 105 are presented here for thefirst time. A large number of IR/X-ray source chance coincidences arefound in this sample; of the 40-50 expected, we have identified 18firmly and have established strong cases for 29 others. Most chancecoincidences involve bright stars or Seyfert galaxies close (inprojection) to IR- bright H II galaxies. Although this work wasmotivated initially by the report that a new class of X-ray-luminous,normal spiral galaxies was to be found in this sample, we find noevidence for such a class. Most of the extragalactic X-ray sources areactive galactic nuclei (AGNs), consistent with the results of previousstudies of X-ray-selected objects. However, many of these AGNs exhibitweak or heavily reddened Seyfert features in their optical spectra. Inaddition, two rare types of AGNs are found in this sample withsurprising frequency: I Zw 1 objects (also called narrow-line Seyfert 1galaxies) and starburst/Seyfert composite galaxies, a new class ofluminous X-ray sources. We have shown that the Boller et al. object202103 - 223434 (= IRAS 20181-2244), reported to be the best example ofa narrow-line quasar, is actually a member of the I Zw 1 class. Theenigmatic starburst/Seyfert composite galaxies have optical spectradominated by the features of H II galaxies but X-ray luminositiestypical for Seyfert galaxies. Close examination of their optical spectrareveals subtle Seyfert signatures: [O III] lines broader than all otherlines in the spectrum and, in some cases, a weak, broad Hαcomponent. Obscuration of the active nucleus is likely to explain theX-ray and optical properties of these objects. We describe a scenario inwhich such optically innocuous, obscured AGNs could comprise animportant new component of the X-ray background.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| 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.
| ROSAT All Sky Survey observations of IRAS galaxies
Cross-correlations are established between 14,708 selected IRAS sourcesand the ROSAT All Sky Survey X-ray sources. The resulting catalog of 244IRAS galaxies positionally coincident with ROSAT X-ray sources ispresented. For 222 of them, optical counterparts could be identified bya comparison with the NASA/IPAC Extragalactic Database. An unexpectedresult was the discovery of several spiral galaxies with luminosities upto 10 exp 43 erg/s, well above those found with the Einstein satellite.
| Neutral hydrogen observations of galaxies in superclusters
Neutral hydrogen observations of spiral galaxies in the Uppsala GeneralCatalog were made with the 91 m telescope in Green Bank. Results of theH I observations are presented for 309 objects north of declination +38deg in the right ascension range between 10 h and 22 h and for a sampleof 46 objects just south of the equator in the region around R.A.between 0 h and 3 h. Many of these objects are outlying members ofsuperclusters and may be useful in the study of deviations from Hubbleflow on supercluster scales. Velocity widths as measured by fivedifferent algorithms are presented along with a profile quality index.
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