Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
The PDS versus Markarian starburst galaxies: comparing strong and weak IRAS emitter at 12 and 25 μm in the nearby Universe
The characteristics of the starburst galaxies from the Pico dos Diassurvey (PDS) are compared with those of the nearby ultraviolet (UV)bright Markarian starburst galaxies, having the same limit in redshift(vh < 7500 km s-1) and absolute B magnitude(MB < -18). An important difference is found: theMarkarian galaxies are generally undetected at 12 and 25 μm in IRAS.This is consistent with the UV excess shown by these galaxies andsuggests that the youngest star-forming regions dominating thesegalaxies are relatively free of dust.The far-infrared selection criteria for the PDS are shown to introduce astrong bias towards massive (luminous) and large size late-type spiralgalaxies. This is contrary to the Markarian galaxies, which are found tobe remarkably rich in smaller size early-type galaxies. These resultssuggest that only late-type spirals with a large and massive disc arestrong emitters at 12 and 25 μm in IRAS in the nearby Universe.The Markarian and PDS starburst galaxies are shown to share the sameenvironment. This rules out an explanation of the differences observedin terms of external parameters. These differences may be explained byassuming two different levels of evolution, the Markarian being lessevolved than the PDS galaxies. This interpretation is fully consistentwith the disc formation hypothesis proposed by Coziol et al. to explainthe special properties of the Markarian SBNG.
| The Radio Galaxy Populations of Nearby Northern Abell Clusters
We report on the use of the NRAO VLA Sky Survey (NVSS) to identify radiogalaxies in 18 nearby Abell clusters. The listings extend from the coresof the clusters out to radii of 3 h-175 Mpc, whichcorresponds to 1.5 Abell radii and approximately 4 orders of magnitudein galaxy density. To create a truly useful catalog, we have collectedoptical spectra for nearly all of the galaxies lacking public velocitymeasurements. Consequently, we are able to discriminate between thoseradio galaxies seen in projection on the cluster and those that are inactuality cluster members. The resulting catalog consists of 329 clusterradio galaxies plus 138 galaxies deemed foreground or backgroundobjects, and new velocity measurements are reported for 273 of theseradio galaxies. The motivation for the catalog is the study of galaxyevolution in the cluster environment. The radio luminosity function is apowerful tool in the identification of active galaxies, as it isdominated by star-forming galaxies at intermediate luminosities andactive galactic nuclei (AGNs) at higher luminosities. The flux limit ofthe NVSS allows us to identify AGNs and star-forming galaxies down tostar formation rates less than 1 Msolar yr-1. Thissensitivity, coupled with the all-sky nature of the NVSS, allows us toproduce a catalog of considerable depth and breadth. In addition tothese data, we report detected infrared fluxes and upper limits obtainedfrom IRAS data. It is hoped that this database will prove useful in anumber of potential studies of the effect of environment on galaxyevolution. Based in part on observations obtained with the Apache PointObservatory 3.5 m telescope, which is owned and operated by theAstrophysical Research Consortium (ARC).
| An Hα survey of eight Abell clusters: the dependence of tidally induced star formation on cluster density
We have undertaken a survey of Hα emission in a substantiallycomplete sample of CGCG galaxies of types Sa and later within 1.5 Abellradii of the centres of eight low-redshift Abell clusters (Abell 262,347, 400, 426, 569, 779, 1367 and 1656). Some 320 galaxies weresurveyed, of which 116 were detected in emission (39 per cent ofspirals, 75 per cent of peculiars). Here we present previouslyunpublished data for 243 galaxies in seven clusters. Detected emissionis classified as `compact' or `diffuse'. From an analysis of the fullsurvey sample, we confirm our previous identification of compact anddiffuse emission with circumnuclear starburst and disc emissionrespectively. The circumnuclear emission is associated either with thepresence of a bar, or with a disturbed galaxy morphology indicative ofongoing tidal interactions (whether galaxy-galaxy, galaxy-group, orgalaxy-cluster). The frequency of such tidally induced (circumnuclear)starburst emission in spirals increases from regions of lower to higherlocal galaxy surface density, and from clusters with lower to highercentral galaxy space density. The percentages of spirals classed asdisturbed and of galaxies classified as peculiar show a similar trend.These results suggest that tidal interactions for spirals are morefrequent in regions of higher local density and for clusters with highercentral galaxy density. The prevalence of such tidal interactions inclusters is expected from recent theoretical modelling of clusters witha non-static potential undergoing collapse and infall. Furthermore, inaccord with this picture, we suggest that peculiar galaxies arepredominantly ongoing mergers. We conclude that tidal interactions arelikely to be the main mechanism for the transformation of spirals to S0sin clusters. This mechanism operates more efficiently in higher densityenvironments, as is required by the morphological type-local surfacedensity (T-Σ) relation for galaxies in clusters. For regions ofcomparable local density, the frequency of tidally induced starburstemission is greater in clusters with higher central galaxy density. Thisimplies that, for a given local density, morphological transformation ofdisc galaxies proceeds more rapidly in clusters of higher central galaxydensity. This effect is considered to be the result of subclustermerging, and could account for the previously considered anomalousabsence of a significant T-Σ relation for irregular clusters atintermediate redshift.
| IRAS galaxies in the Perseus cluster
We cross-correlate the optical catalogue of galaxies in the field of thePerseus cluster (Abell 426) with IRAS PSC sources. The optical cataloguecomprises data on 660 galaxies brighter than B25 ~ 19.5(Brunzendorf & Meusinger 1999). A sample of 19 IRAS galaxies isfound. According to their redshifts, 17 galaxies are likely members ofthe Perseus cluster, two are background galaxies. The sample-averagedFIR excess is higher than expected for normal galaxies. The opticalmorphology of the IRAS galaxies is evaluated on CCD images taken in theB band at a seeing of about 1'', complemented by CCD images taken in theredshifted Hα band or in the R band. Individual descriptions arepresented along with the B band images for all of the IRAS galaxies. Asubstantial fraction of the galaxies in the IRAS sample exhibit signsfor morphological distortion. A correlation between the FIR activity andthe strength of distortion is indicated. On the other hand, there areapproximately as many disturbed/interacting galaxies in the Perseuscluster region without IRAS counterparts as IRAS galaxies. The IRASgalaxies are much less concentrated towards the cluster centre thantypical bright cluster galaxies. For the distorted non-IRAS galaxies,such a trend is less pronounced. These differences may be related torapid stripping of gas as galaxies enter the cluster.
| 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 galaxy cluster Abell 426 (Perseus). A catalogue of 660 galaxy positions, isophotal magnitudes and morphological types
We present a homogeneous catalogue of galaxies in the field of thenearby galaxy cluster A 426 (Perseus) based on a survey of digitisedSchmidt plates taken with the Tautenburg 2 m telescope in the B band.Accurate positions, morphological types, B25 isophotalmagnitudes, angular radii and position angles are given for 660 galaxieswithin a field of about 10 square-degrees, centred on alpha = 3() h 21()min, delta = 41degr 33' (J2000). When available, the radial velocity andthe most common name taken from NED or PGC are included. The cataloguecomprises galaxies brighter than B25~19.5. The estimatedlimit of completeness is B25~18. Two thirds of the galaxiesare published for the first time. The galaxy positions are measured witha mean accuracy of 0farcs5 , the photometric accuracy is of the order of0.1 to 0.2 mag depending on image crowding and galaxy shape.Morphological properties were evaluated from the visual inspections ofboth deep images obtained from the digital co-addition of a large numberof plates and higher-resolution images from single plates taken undergood seeing conditions. The superimposed images unveil faint structuresdown to mu_B ~ 27 mag arcsec(-2) . The catalogue is applied to a studyof statistical properties of the galaxies in A 426: projecteddistribution of morphological types, segregation of morphological types,position of the cluster centre, distribution of galaxy position angles,type-dependent luminosity functions, and total B-luminosity of the thecluster. In agreement with previous studies, we find a relativespiral-deficiency in the central region (r <~ 30'). The percentage ofidentified S+Irr increases, however, increases from 30% in the centre tomore than 50% in the outer parts. The projected distributions of early-and late-type galaxies are not co-centred. The total luminosity of allsupposed member galaxies in the surveyed area is estimated to(6.5+/-0.9)\ 10(12) x h50(-2) blue solar luminosities. We donot analyse in detail possible substructures in the projecteddistribution of galaxies. However, we found a pronounced clump ofgalaxies at alpha (J2000.0) = 3() h20fm4 , delta (J2000.0) = 43degr4 ',which is shown to be a background cluster at z~ 0.050. The catalogue isonly available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html } \fnmsep \thanks{ Based onobservations made with the 2\,m telescope of the ThüringerLandessternwarte Tautenburg, Germany, and with the 2.2\,m telescope ofthe German-Spanish Astronomical Centre, Calar Alto, Spain.
| The Pico DOS Dias Survey Starburst Galaxies
We discuss the nature of the galaxies found in the Pico dos Dias Survey(PDS) for young stellar objects. The PDS galaxies were selected from theIRAS Point Source catalog. They have flux density of moderate or highquality at 12, 25, and 60 μm and spectral indices in the ranges -3.00<= alpha(25, 12) <= + 0.35 and -2.50 <= alpha(60, 25) <=+0.85. These criteria allowed the detection of 382 galaxies, which are amixture of starburst and Seyfert galaxies. Most of the PDS Seyfertgalaxies are included in the catalog of warm IRAS sources by de Grijp etal. The remaining galaxies constitute a homogeneous sample of luminous[log F (L_B/L_ȯ) = 9.9 +/- 0.4] starburst galaxies, 67% of whichwere not recognized as such before. The starburst nature of the PDSgalaxies is established by comparing their L_IR/L_B ratios and IRAScolors with a sample of emission-line galaxies from the literaturealready classified as starburst galaxies. The starburst galaxies show anexcess of FIR luminosity, and their IRAS colors are significantlydifferent from those of Seyfert galaxies-99% of the starburst galaxiesin our sample have a spectral index alpha(60, 25) < -1.9. As opposedto Seyfert galaxies, very few PDS starbursts are detected in X-rays. Inthe infrared, the starburst galaxies form a continuous sequence withnormal galaxies. But they generally can be distinguished from normalgalaxies by their spectral index alpha(60, 25) > -2.5. This colorcutoff also marks a change in the dominant morphologies of the galaxies:the normal IRAS galaxies are preferentially late-type spirals (Sb andlater), while the starbursts are more numerous among early-type spirals(earlier than Sbc). This preference of starbursts for early-type spiralsis not new, but a trait of the massive starburst nucleus galaxies(Coziol et al.). As in other starburst nucleus galaxy samples, the PDSstarbursts show no preference for barred galaxies. No difference isfound between the starbursts detected in the FIR and those detected onthe basis of UV excess. The PDS starburst galaxies represent the FIRluminous branch of the UV-bright starburst nucleus galaxies, with meanFIR luminosity log (L_IR/L_ȯ) = 10.3 +/- 0.5 and redshifts smallerthan 0.1. They form a complete sample limited in flux in the FIR at 2 x10^-10 ergs cm^-2 s^-1.
| The Interchangeability of CO and H I in the Tully-Fisher Relation
We investigate the viability and precision of using ^12CO (J = 1 -->0) emission lines from galaxies in lieu of 21 cm emission in theTully-Fisher distance indicator (TF). Here we combine CO data gatheredspecifically for Tully-Fisher analysis with I-band photometry (both newand from the literature) for cluster galaxies between 3500 and 8000 kms^-1 and compare the luminosity-line width relation using CO with theresults of recent, large TF surveys using H i and Hα. We cull someCO data as suggested by previously published numerical simulations andfind that CO line widths, with corrections for turbulence andnoise-broadening on the order of 35 km s^-1, behave identically to H iand Hα in luminosity-line width analyses. We also examine therelation between CO line shapes and other parameters of the galaxies.
| Observations of (C-12)O (J = 1-0) in 44 cluster galaxies
We present (C-12)O (J = 10) (2.6 mm, 115 GHz) spectra from 44 galaxiesin clusters between 3500 and 8000 km/s. The data were obtained using theNRAO 12 m telescope at Kitt Peak. Forty galaxies are detected. We deducemolecular gas masses from the line integrated intensities and upperlimits for the four nondetections. Although the sample's first inclusioncriterion is that a source have 60 m flux greater than 350 mJy, thegalaxies in this survey are found to be neither ultraluminous in the FIRnor particularly rich in molecular gas, nor do they exhibit evidence ofinteractions. Neither the molecular gas mass nor the far-IR luminosityshows variations as functions of the galaxies' proximity to the clustercores. Because the CO line widths and central velocities agree overallwith the 21 cm widths and redshifts for these galaxies, we argue that COspectra could be used in lieu of H I spectra for Tully-Fishercalculations.
| 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 Northern Milky Way
We made a search for IRAS galaxies behind the Northern Milky Way byinfrared selection using IRAS Point Source Catalog and visual inspectionon POSS (Palomar Observatory Sky Survey) paper prints, and carried out aredshift survey of the identified objects. This paper presents a catalogof 649 IRAS galaxies with f_60_>=0.6 Jy between l=150deg and 240degat |b|<=15deg , which contains 254 newly identified galaxies and 188newly measured radial velocities. Due to galactic extinction, our sampleis a lower limit sample of the flux limited sample of IRAS galaxies, butit can give some information on the distribution of galaxies in theregion perpendicular to the Supergalactic Plane. We confirm two regionswith enhanced density at l=~160deg , cz=~5000 km/s and l=~190deg ,cz=~5000 km/s and at least two possible voids.
| 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.
| Models for infrared emission from IRAS galaxies
The far-infrared spectra of galaxies detected in four wavelength bandsby IRAS have been modeled in terms of a cool disk component, a warmerstarburst component, and a Seyfert component peaking at 25 microns.Although the models are found to fit the observed spectra of non-Seyfertand several Seyfert galaxies, a more complex geometry for the dustdistribution is indicated for NGC 1068 and many other Seyfert galaxies.In some cases, the dust in the narrow-line region has a nonsphericallysymmetric geometry.
| The pattern of gas deficiency in cluster spirals - The correlation of H I and X-ray properties
The neutral hydrogen content of spiral galaxies is investigated as afunction of their location with six nearby rich clusters. Previousfindings that H I deficiency varies with projected radius from thecluster center are confirmed, but no correlation between H I depletionand velocity relative to the cluster is seen. The dependence of H Ideficiency on radius is monotonic; the most H I-poor objects are locatedclose to the cluster center. The current data, however, cannot be usedto distinguish between inbred and evolutionary gas deficiency mechanismsor among different environmental processes. Indications are found thatenvironmental effects on spirals, if present at all, only modify theimprint left at the time of cluster formation. Obstacles and possibleremedies to the current limitations are discussed.
| The dynamics of rich clusters of galaxies. II - The Perseus cluster
The dynamics of the Perseus cluster are analyzed using self-consistentequilibrium analytical models. Using existing data in the literatureplus new radial velocities reported here, composite surface density andvelocity dispersion profiles are derived. These profiles have beencompared with dynamical models described by Kent and Gunn (1982). Thebest fit suggest the presence of a significant degree of anisotropy inthe velocity distribution: galaxy orbits are constrained to pass withina radius of seven cluster radii, or 1.3 deg of the cluster center. ForHubble constant = 50, a core radius of 340 kpc 11 arcmin and a mass tovisual light ratio M/L = 300 are found. Using these results, X-rayobservations of the intracluster medium in Perseus are reanalyzed. Apreviously noted discrepancy between the observed temperature of the hotgas and the cluster velocity dispersion is reduced but not eliminated. Acooling accretion flow previously deduced to exist in this cluster isshown to extend to only about one-third of the cluster radius.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
Katalógusok és elnevezések:
|
