Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Rotational Widths for Use in the Tully-Fisher Relation. I. Long-Slit Spectroscopic Data
We present new long-slit Hα spectroscopy for 403 noninteractingspiral galaxies, obtained at the Palomar Observatory 5 m Hale telescope,which is used to derive well-sampled optical rotation curves. Becausemany of the galaxies show optical emission features that aresignificantly extended along the spectrograph slit, a technique wasdevised to separate and subtract the night sky lines from the galaxyemission. We exploit a functional fit to the rotation curve to identifyits center of symmetry; this method minimizes the asymmetry in thefinal, folded rotation curve. We derive rotational widths using bothvelocity histograms and the Polyex model fit. The final rotational widthis measured at a radius containing 83% of the total light as derivedfrom I-band images. In addition to presenting the new data, we use alarge sample of 742 galaxies for which both optical long-slit and radioH I line spectroscopy are available to investigate the relation betweenthe H I content of the disks and the extent of their rotation curves.Our results show that the correlation between those quantities, which iswell established in the case of H I-poor galaxies in clusters, ispresent also in H I-normal objects: for a given optical size, starformation can be traced farther out in the disks of galaxies with largerH I mass.
| A sample of X-ray emitting normal galaxies from the BMW-HRI Catalogue
We obtained a sample of 143 normal galaxies with X-ray luminosity in therange 1038{-}1043 erg s-1 from thecross-correlation of the ROSAT HRI Brera Multi-scale Wavelet (BMW-HRI)Catalogue with the Lyon-Meudon Extragalactic Database (LEDA). We findthat the average X-ray properties of this sample are in good agreementwith those of other samples of galaxies in the literature. We selected acomplete flux limited serendipitous sample of 32 galaxies from which wederived the log N-log S distribution of normal galaxies in the fluxrange 1.1{-} 110 × 10-14 erg cm-2s-1. The resulting distribution is consistent with theEuclidean -1.5 slope. Comparisons with other samples, such as theExtended Medium Sensitivity Survey, the ROSAT All Sky Survey, theXMM-Newton/2dF survey, and the Chandra Deep Field Survey indicate thatthe log N -log S distribution of normal galaxies is consistent with aEuclidean slope over a flux range of about 6 decades.
| The field surrounding NGC 7603: Cosmological or non-cosmological redshifts?
We present new observations of the field surrounding the Seyfert galaxyNGC 7603, where four galaxies with different redshifts - NGC 7603(z=0.029), NGC 7603B (z=0.057) and two fainter emission line galaxies(z=0.245 and z=0.394) - are apparently connected by a narrow filament,leading to a possible case of anomalous redshift. The observationscomprise broad and narrow band imaging and intermediate resolutionspectroscopy of some of the objects in the field. The new data confirmthe redshift of the two emission-line objects found within the filamentconnecting NGC 7603 and NGC 7603B, and settles their type with betteraccuracy. Although both objects are point-like in ground based images,using HST archive images we show that the objects have structure with aFWHM = 0.3-0.4 arcsec. The photometry in the R-band obtained duringthree different campaigns spread over two years does not show any signsof variability in these objects above 0.3-0.4 mag. All the aboveinformation and the relative strength and width of the main spectrallines allow us to classify these as HII galaxies with very vigorous starformation, while the rest of the filament and NGC 7603B lack starformation. We delineate the halo of NGC 7603 out to 26.2mag/arcsec2 in the Sloan r band filter and find evidence forstrong internal distortions. New narrow emission line galaxies atz=0.246, 0.117 and 0.401 are also found at respectively 0.8, 1.5 and 1.7arcmin to the West of the filament within the fainter contour of thishalo. We have studied the spatial distribution of objects in the fieldwithin 1.5 arcmin of NGC 7603. We conclude that the density of QSOs isroughly within the expected value of the limiting magnitude of ourobservations. However, the configuration of the four galaxies apparentlyconnected by the filament appears highly unusual. The probability ofthree background galaxies of any type with apparent B-magnitudes up to16.6, 21.1 and 22.1 (the observed magnitudes, extinction correctionincluded) being randomly projected on the filament of the fourth galaxy(NGC 7603) is ≈ 3× 10-9. Furthermore, the possibledetection of very vigorous star formation observed in the HII galaxiesof the filament would have a low probability if they were backgroundnormal-giant galaxies; instead, the intensity of the lines is typical ofdwarf HII galaxies. Hence, a set of coincidences with a very lowprobability would be necessary to explain this as a fortuitousprojection of background sources. Several explanations in terms ofcosmological or non-cosmological redshifts are discussed.
| 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
| Hot and Cold Gas in Early-Type Spirals: NGC 3623, NGC 2775, and NGC 1291
We have studied the distribution of cool, warm, and hot interstellarmatter in three of the nearest bright Sa galaxies. New X-ray data forNGC 1291, the object with the most prominent bulge, confirm earlierresults that the ISM in the bulge is dominated by hot gas. NGC 3623 hasa lesser amount of hot gas in the bulge but has both molecular gas andionized hydrogen in the central regions. NGC 2775 has the leastprominent bulge; its X-ray emission is consistent with an origin inX-ray binary stars, and there is a strict upper limit on the amount ofmolecular present in the bulge. All three galaxies have a ring ofneutral hydrogen in the disk. NGC 3623 and NGC 2775 each have inaddition a molecular ring coincident with the hydrogen ring. We concludethat even within the morphological class Sa there can be significantdifferences in the gas content of the bulge, with the more massivebulges being likely to contain hot, X-ray-emitting gas. We discuss thepossibility that the X-ray gas is part of a cooling flow in which coolgas is produced in the nucleus.
| 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.
| Dark matter in early-type spiral galaxies: the case of NGC 2179 and of NGC 2775
We present the stellar and ionized-gas velocity curves andvelocity-dispersion profiles along the major axis for six early-typespiral galaxies. Two of these galaxies, namely NGC 2179 and NGC 2775,are particularly suited for the study of dark matter halos. Using theirluminosity profiles and modeling their stellar and gaseous kinematics,we derive the mass contributions of the luminous and the dark matter tothe total potential. In NGC 2179 we find that the data (measured out toabout the optical radius R_opt) unambiguously require the presence of amassive dark halo. For the brighter and bigger object NGC 2775, we canrule out a significant halo contribution at radii R <~ 0.6 R_opt.Although preliminary, these results agree with the familiar massdistribution trend known for late-type spirals of comparable mass. Basedon observations carried out at ESO, La Silla (Chile) (ESO N. 52, 1-020)and on observations obtained with the VATT: the Alice P. LennonTelescope and the Thomas J. Bannan Astrophysics Facility. Tables 4 to 42are only 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.
| The amorphous galaxy NGC 2777 - H I evidence for tidal interaction with a faint companion
NGC 2777 is an amorphous galaxy possessing the classic signature of anA-type spectrum with superposed emission lines. There is no opticalevidence for an interaction, but observations of the neutral hydrogen inthis system reveal an H I bridge between NGC 2777 and U3, a companionthat is 3 mag fainter. FIR observations indicate that the current rateof massive star formation in NGC 2777 is low, but the optical spectraindicate that it must have been significantly higher in the recent past.We were unable to detect CO in either galaxy. We also consider a sampleof 10 amorphous galaxies, all showing A-type absorption spectra: ninefrom the Revised Shapley-Ames Catalog, plus NGC 2777. All show optical/HI interaction and/or peculiar velocity fields, supporting the view thatamorphous characteristics are the result of interaction. For some of thegalaxies, the interacting companion is much fainter than the amorphoussystem, which indicates that previous concerns raised by the existenceof isolated amorphous galaxies may have been premature.
| Catalogue of HI maps of galaxies. II. Analysis of the data
We use some of the maps of the catalogue presented in Paper I to providesome evidence for global conditions that must be fulfilled by thegalaxies to have extended hydrogen. For this purpose, we tried to findpossible connections between the HI gas extension and other propertiesof the galaxies (morphological type, surface brightness, gas density,etc.). With isophotal hydrogen diameters of a large sample, we couldobserve that optically smaller galaxies seem to have greater relative HIextensions. By means of the relation with the apparent HI surfacedensity, we found an expression that should provide a rough estimate ofthe gas extension. With respect to the dependence on morphological type,we could not find any significant correlation either for the real HIsurface density or the relative gas extension. Nevertheless, whereas forspiral and irregular galaxies the real HI surface density exhibits abroad range of values, the values are rather lower for elliptical and S0galaxies. Table 1 is also available in electronic form at the CDS viaanonymous ftp 130.79.128.5 or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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
| NGC 2777: an Amorphous Galaxy With a Faint, Tidally Interacting Companion
Amorphous galaxies are a relatively rare morphological type representingabout one percent of catalogued galaxies. Several are well knownexamples of tidal interaction and display extensive HI distortions andstreamers. The M82-M81 and the NGC 3077-M81 systems are representative.It is such prominent interaction that has prompted the suggestion thatmaterial captured by the soon-to-be amorphous galaxy is responsible forthe formation of such systems. NGC 2777 is an amorphous galaxy of 14thmagnitude and is a member of the sparse NGC 2775 Group. It is 11 arcmindistant (55 kpc) from NGC 2775. An Arecibo telescope map of this group(Haynes, AJ 86, 1126, 1981) shows an extension of the HI of NGC 2777.The extension is generally towards NGC 2775 but not quite along the lineto it. The latter galaxy is a near face-on Sa system with no apparent HIextension or anomaly. The radial velocities of the two systems differ by140 km/s. A recent VLA map of the complex shows that the HI around NGC2777 is actually extended in the direction of an anonymous galaxy whichlies at a distance of about 3.5 arcmin. The presence of this companionis mentioned in the Notes to the UGC. Arp and Sulentic(ApJ,375,569,1991) have discussed the relationship between this objectand NGC 2777. Following Arp, we will call this object U3. The radialvelocities of the HI in NGC 2777 and U3 differ by less than 100 km/s.The HI contours at the 20 mJy/beam level in both systems are asymmetricand point to one another along the line connecting their centers. Theyare clearly interacting and this interaction represents another instanceof an amorphous galaxy showing tidal effects in its HI. However, in thisinstance the more luminous (more massive?) galaxy displays the amorphouscharacteristics unlike, e.g., M82/M81 and NGC 3077/M81. The character ofU3 is unknown, but additional observations of it are in progress.
| 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.
| Flat spacetime cosmology - A unified framework for extragalactic redshifts
It is known that the standard Friedmann cosmology with k = 0 can bedescribed equivalently in a conformal frame in which the spacetime isMinkowskian but all particle masses uniformly scale with epoch. In aMachian theory of gravity this spacetime dependence of mass isunderstood in terms of inertial interactions. This picture is shown tobe more versatile than standard cosmology because it allows one tointerpret objects of anomalously high redshift to be 'young' objectswhose particle masses are lagging behind the universal mass function. Wediscuss here a variety of extragalactic phenomena within the frameworkof this model and show that these can be understood without recourse toadjustable parameters such as evolution, cosmological constant, etc.
| 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.
| Redshifts of high-luminosity stars - The K effect, the Trumpler effect and mass-loss corrections
The Trumpler effect is demonstrated in B and A supergiants in h + ChiPersei, as well as in other associations of young luminous stars. TheK-Trumpler effect is also shown in O, B, and A supergiants in theMagellanic Clouds, as well as in nearby galaxies such as NGC 1569 and2777 and in blue irregular variables in M31 and M33. Mass outflow inluminous stars is shown to require an average correction of about 20km/s and to increase the excess redshifts of the stars in the MagellanicClouds to a significance level of 6 sigma. Completely empirical andindependent measurements show that mass-loss corrections of this sizeare required on average for supergiants in both the SMC and LMC and alsoin the Milky Way.
| An X-ray catalog and atlas of galaxies
An X-ray catalog and atlas of galaxies observed with the EinsteinObservatory imaging instruments (IPC and HRI) are presented. The catalogcomprises 493 galaxies, including targets of pointed observations, andRSA or RC2 galaxies serendipitously included in Einstein fields. A totalof 450 of these galaxies were imaged well within the instrumentalfields, resulting in 238 detections and 2123 sigma upper limits. Theother galaxies were either at the edge of the visible field of view orconfused with other X-ray sources. For these a rough measure of theirX-ray emission is also given. The atlas shows X-ray contour maps ofdetected galaxies superposed on optical photographs and givesazimuthally averaged surface brightness profiles of galaxies detectedwith a high signal-to-noise ratio.
| Velocity differences in binary galaxies. I - Suggestions for a nonmonotonic, two-component distribution
A compilation of published high-precision velocities for 107 isolatedgalaxies is presented and used to obtain the distribution function oftheir velocity differences. The distribution shows a peak at the zerodifference as expected, but it also exhibits a preference for valuesnear 72 km/2. The distribution function declines smoothly beyond about72 km/s, with no significant peaks at multiples of 72 km/s, as claimedby Tifft (1977, 1980, 1982). It is argued that criteria for selectionprocedures on binary galaxy samples which are defined on the basis oftoo narrow a projected separation in the sky can produce a nonmonotonicdistribution if the orbits are eccentric. Such orbits can produce astrong secondary peak only if the level of incompleteness inbinary-galaxy samples is quite high, suggesting that the presentstatistical estimates of the masses of binary galaxies should bereevaluated.
| The properties of NGC 2777 - Are companion galaxies young?
NGC 2777 is shown to be typical of a class of galaxies that are composedpredominantly of recently formed stars and that are companions to largergalaxies. It is argued that star formation acativity is not stimulatedby gravitational or collisional encounter with the main galaxy. Evidenceis discussed which suggests that these kinds of companions are formed inejection events from older galaxies and that they are more recentlycreated galaxies. Star formation in jets is proposed as the explanationfor the strong, general correlation between nonthermal and infraredemission in galaxies.
| Analysis of groups of galaxies with accurate redshifts
Arecibo radio telescope redshift measurements have been obtained forover 100 galaxies in more than 40 different groups which generallyconsist of a large spiral galaxy with one or more companions. This setof data is supplemented with over 160 galaxies in more than 40 groupswhose dominant galaxy is brighter than 11.8 mag. An analysis of theentire sample indicates that typical structure in extragalactic space isone in which a large central galaxy has smaller and fainter companionsextending from about 20-900 kpc around. The companion galaxies in thesegroups have significantly higher redshifts than the brightest galaxy inthe group, confirming previous studies in whose results the companiongalaxies are systematically redshifted with respect to the dominantgalaxy.
| 21-cm observations of galaxies in groups and multiplets
Measures at the 21-cm line of neutral hydrogen are reported for a largesample of individual galaxies in groups as well as for interactingmultiple-component systems. The observations of single galaxies weredesigned to study differential redshifts within groups. Observations ofinteracting systems were undertaken to obtain system redshifts as wellas 21-cm profile morphology. The data, which will be used in futureanalyses, are presented here along with a discussion of interactionmorphology from the 21-cm profile point of view. Together the profilesamples encompass the full range of dynamical states in which the gascomponents of galaxies are observed, from relaxed to violentlydisrupted.
| 21-cm line observations of 59 lenticular and spiral galaxies
Fifty-nine lenticular and spiral galaxies have been observed with theNancay Radiotelescope. Forty-one have been detected and for nine objectsdetected in more than one position the HI diameter is given. Thecomparison between HI fluxes observed with the Nancay Radiotelescope andthose obtained with other radiotelescopes shows a good generalagreement, implying an uncertainty on the HI flux measurements about 3Jy-km/s, whereas the few obvious disagreements observed are due toconfusion or to anomalous HI extensions.
| X-ray observations of peculiar galaxies with the Einstein Observatory
The results of X-ray observations with the Einstein Observatory of 33galaxies are presented. Almost all of these galaxies, some of which liein groups and in interactive pairs, display disturbed morphologies. Nouniform, well-defined selection criterion can describe the samplegalaxies, but almost all lie in a region of the optical color/colordiagram that suggests that they are experiencing bursts of starformation. This region is compatible with the locus of Markariangalaxies. The observed sample and the X-ray data are presented, and theX-ray data are discussed and compared with the optical and radioproperties of the galaxies. It is concluded that nuclear activity is notthe predominant source of X-rays in late-type peculiar galaxies and thatthe X-ray emission is likely to originate from the Population I galacticcomponent, in particular binary sources and possible young SNR's.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
Katalógusok és elnevezések:
|
