WIKISKY.ORG
 Home Getting Started To Survive in the Universe News@Sky Astro Photo The Collection Forum Blog New! FAQ Press Login

# NGC 6156

Contents

### Images

 - No Images Found -

DSS Images   Other Images

### Related articles

 Classification of Spectra from the Infrared Space Observatory PHT-S DatabaseWe have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA). The IRAS Revised Bright Galaxy SampleIRAS flux densities, redshifts, and infrared luminosities are reportedfor all sources identified in the IRAS Revised Bright Galaxy Sample(RBGS), a complete flux-limited survey of all extragalactic objects withtotal 60 μm flux density greater than 5.24 Jy, covering the entiresky surveyed by IRAS at Galactic latitudes |b|>5°. The RBGS includes629 objects, with median and mean sample redshifts of 0.0082 and 0.0126,respectively, and a maximum redshift of 0.0876. The RBGS supersedes theprevious two-part IRAS Bright Galaxy Samples(BGS1+BGS2), which were compiled before the final(Pass 3) calibration of the IRAS Level 1 Archive in 1990 May. The RBGSalso makes use of more accurate and consistent automated methods tomeasure the flux of objects with extended emission. The RBGS contains 39objects that were not present in the BGS1+BGS2,and 28 objects from the BGS1+BGS2 have beendropped from RBGS because their revised 60 μm flux densities are notgreater than 5.24 Jy. Comparison of revised flux measurements forsources in both surveys shows that most flux differences are in therange ~5%-25%, although some faint sources at 12 and 25 μm differ byas much as a factor of 2. Basic properties of the RBGS sources aresummarized, including estimated total infrared luminosities, as well asupdates to cross identifications with sources from optical galaxycatalogs established using the NASA/IPAC Extragalactic Database. Inaddition, an atlas of images from the Digitized Sky Survey with overlaysof the IRAS position uncertainty ellipse and annotated scale bars isprovided for ease in visualizing the optical morphology in context withthe angular and metric size of each object. The revised bolometricinfrared luminosity function, φ(Lir), forinfrared-bright galaxies in the local universe remains best fit by adouble power law, φ(L)~Lα, withα=-0.6(+/-0.1) and α=-2.2(+/-0.1) below and above thecharacteristic'' infrared luminosityL*ir~1010.5Lsolar,respectively. A companion paper provides IRAS High Resolution (HIRES)processing of over 100 RBGS sources where improved spatial resolutionoften provides better IRAS source positions or allows for deconvolutionof close galaxy pairs. A Search for H2O Maser Emission in Southern Active Galactic Nuclei and Star-forming Galaxies: Discovery of a Maser in the Edge-on Galaxy IRAS F01063-8034We report the cumulative results of five surveys for H2Omaser emission at 1.35 cm wavelength in 131 active galactic nuclei(AGNs) and star-forming galaxies, conducted at the Parkes Observatorybetween 1993 and 1998. We detected one new maser, in the edge-on galaxyIRAS F01063-8034, which exhibits a single ~0.1 Jy spectral feature at4282+/-6 km s-1 (heliocentric) with an unusually large54+/-16 km s-1 half-power full width. The centroid velocityof the emission increased to 4319.6+/-0.6 km s-1 (38+/-2 kms-1 width) over the 13 days between discovery andconfirmation of the detection. A similarly broad-line width and largechange in velocity has been noted for the maser in NGC 1052, wherein jetactivity excites the emission. Neither optical spectroscopy,radio-infrared correlations, nor infrared colors provide compellingevidence of unusual activity in the nucleus of IRAS F01063-8034. Sincethe galaxy appears to be outwardly normal at optical and infraredwavelengths, detection of an H2O maser therein is unique. Themaser emission is evidence that the galaxy harbors an AGN that isprobably obscured by the edge-on galactic disk. The detection highlightsthe possibility that undetected AGNs could be hidden in other relativelynearby galaxies. No other maser emission features have been identifiedat velocities between 3084 and 6181 km s-1. A catalogue of galaxies behind the southern Milky Way. II. The Crux and Great Attractor regions (l~ 289o to 338o)In this second paper of the catalogue series of galaxies behind thesouthern Milky Way, we report on the deep optical galaxy search in theCrux region (289o <= l <= 318o and-10o <= b <= 10o) and the Great Attractorregion (316o <= l <= 338o and-10o <= b <= 10o}). The galaxy cataloguesare presented, a brief description of the galaxy search given, as wellas a discussion on the distribution and characteristics of the uncoveredgalaxies. A total of 8182 galaxies with major diameters D >~ 0.2arcmin were identified in this ~ 850 square degree area: 3759 galaxiesin the Crux region and 4423 galaxies in the Great Attractor region. Ofthe 8182 galaxies, 229 (2.8%) were catalogued before in the optical (3in radio) and 251 galaxies have a reliable (159), or likely (92)cross-identification in the IRAS Point Source Catalogue (3.1%). A numberof prominent overdensities and filaments of galaxies are identified.They are not correlated with the Galactic foreground extinction andhence indicative of extragalactic large-scale structures. Redshiftsobtained at the South African Astronomical Observatory (SAAO) for 518 ofthe newly catalogued galaxies in the Crux and Great Attractor regions(Fairall et al. \cite{Fairall98}; Woudt et al. \cite{Woudt99}) confirmdistinct voids and clusters in the area here surveyed. With this opticalgalaxy search, we have reduced the width of the optical Zone ofAvoidance'' for galaxies with extinction-corrected diameters larger than1.3 arcmin from extinction levels AB >= 1.0m toAB >= 3.0m: the remaining optical Zone of Avoidance is nowlimited by | b | <~ 3o (see Fig. \ref{cruxf1new}). The twooptical catalogues and their respective listings of IRAScross-identifications are available in electronic format at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/380/441 Global physical conditions of the interstellar medium in nearby galaxiesFar-infrared spectra (43-197 mu m) of 34 nearby galaxies obtained by theLong Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory(ISO) were analyzed to investigate the general properties ofinterstellar matter in galaxies. The present sample includes not onlynormal galaxies but also starbursts and active galactic nuclei (AGNs).Far-infrared forbidden lines, such as [C Ii]158 mu m, [O I]63 mu m, [NIi]122 mu m, and [O Iii]88 mu m, were detected in most of the samplegalaxies. [O I]145 mu m line was detected in 13 galaxies. The linefluxes of [C Ii]158 mu m and [N Ii]122 mu m relative to the totalfar-infrared flux (FIR) decrease as the far-infrared color becomesbluer, while the ratio of the [O I]63 mu m flux to FIR does not show asystematic trend with the color. The [O Iii]88 mu m to FIR ratio shows alarge scatter with a weak trend of increase with the color. AGNs do notshow any distinguishable trend from normal and starburst galaxies in thefar-infrared spectra, suggesting that the far-infrared emission ismainly driven by star-formation activities even in AGNs. We estimate thephysical conditions of photodissociation regions (PDRs) in the samplegalaxies, such as the far-ultraviolet radiation field intensityG0 and the gas density n by assuming that all the observed [OI]63 mu m and far-infrared continuum emissions come from PDRs.Comparison with PDR models indicates that G0 ranges from102-104 and n ~ 102-104cm-3. The present results also suggest that n variesproportionally with G0. The ratio of [C Ii] 158 mu m to CO(J=1-0) line emission supports the linear increase in n withG0. We estimate that about a half of [C Ii]158 mu m emissionoriginates from PDRs and attribute the rest to the emission as comingfrom low-density diffuse ionized gas. The estimated intensity of [CIi]158 mu m from the ionized gas is compatible with the observedintensity of [N Ii]122 mu m if both lines come from the same diffuseionized gas. The present analysis suggests that the decrease in [CIi]158 mu m/FIR with the far-infrared color may not be accounted for bythe decrease in the photoelectric heating efficiency owing to theincrease in positive charges of dust grains because a measure of theefficiency, G0/n, is found to stay constant with thefar-infrared color. Instead the decrease can be interpreted in terms ofeither the increase in the collisional de-excitation of the [C Ii]transition due to the increase in the gas density or the decrease in theionized component relative to the far-infrared intensity suggested bythe decrease in [N Ii]122 mu m/FIR. Based on the present analysis, wederive average relations of the far-infrared color with G0and n in galaxies, which can be applied to the investigation ofinterstellar matter in distant galaxies. Based on observations with ISO,an ESA project with instruments funded by ESA Member States (especiallythe PI countries: France, Germany, The Netherlands and the UK) and withthe participation of ISAS and NASA. The impact of bars on the mid-infrared dust emission of spiral galaxies: global and circumnuclear propertiesWe study the mid-infrared properties of a sample of 69 nearby spiralgalaxies, selected to avoid Seyfert activity contributing a significantfraction of the central energetics, or strong tidal interaction, and tohave normal infrared luminosities. These observations were obtained withISOCAM, which provides an angular resolution of the order of 10arcsec(half-power diameter of the point spread function) and low-resolutionspectro-imaging information. Between 5 and 18 mu m, we mainly observetwo dust phases, aromatic infrared bands and very small grains, both outof thermal equilibrium. On this sample, we show that the globalF15/F_7 colors of galaxies are very uniform, the onlyincrease being found in early-type strongly barred galaxies, consistentwith previous IRAS studies. The F15/F_7 excesses areunambiguously due to galactic central regions where bar-inducedstarbursts occur. However, the existence of strongly barred early-typegalaxies with normal circumnuclear colors indicates that therelationship between a distortion of the gravitational potential and acentral starburst is not straightforward. As the physical processes atwork in central regions are in principle identical in barred andunbarred galaxies, and since this is where the mid-infrared activity ismainly located, we investigate the mid-infrared circumnuclear propertiesof all the galaxies in our sample. We show how surface brightnesses andcolors are related to both the available molecular gas content and themean age of stellar populations contributing to dust heating. Therefore,the star formation history in galactic central regions can beconstrained by their position in a color-surface brightness mid-infrareddiagram. Based on observations with ISO, an ESA project with instrumentsfunded by ESA Member States (especially the PI countries: France,Germany, the Netherlands and the UK) and with the participation of ISASand NASA. Extragalactic large-scale structures behind the southern Milky Way. III. Redshifts obtained at the SAAO in the Great Attractor regionIn the third of a series of papers on large-scale structures behind thesouthern Milky Way, we report here on redshifts obtained at the SouthAfrican Astronomical Observatory (SAAO) in the Great Attractor region(318deg <~ l <~ 340deg , |b| <= 10deg , Woudt 1998). Thisregion encompasses the peak in the reconstructed mass density field,associated with the Great Attractor (Kolatt et al. 1995, Dekel et al.1998) and covers the crossing of the Supergalactic Plane with theGalactic Plane. Our deep optical galaxy search in the Zone of Avoidance(ZOA) in this region (Woudt 1998) has resulted in the detection of 4423galaxies with observed diameters larger than 0.2 arcmin. We haveobtained reliable redshifts for 309 galaxies of the 4423 galaxies withthe Unit'' spectrograph (first with a Reticon, then with a CCDdetector) at the 1.9-m telescope of the SAAO. An additional 13 tentativeredshifts are presented. Before our survey, 127 galaxies had apreviously recorded redshift (NED and SRC96). Given a small overlap withthe literature (44 galaxies), we present here redshifts for 265 galaxiesthat had no previous recorded velocity. In addition, we present centralvelocity dispersion (sigma_o ) measurements for 34 galaxies in ACO 3627.It is known that the Great Attractor (GA) region is overdense ingalaxies at a redshift-distance of v ~ 5000 {km s-1 }(Fairall 1988, Dressler 1991, Visvanathan & Yamada 1996, di Nella etal. 1997). We realise here, however, that the Great Attractor region isdominated by ACO 3627 (hereafter referred to as the Norma cluster), ahighly obscured, nearby and massive cluster of galaxies close to theplane of the Milky Way (l, b, v) = (325.3deg , -7.2deg , 4844 {kms-1 }) (Kraan-Korteweg et al. 1996, Woudt 1998). Previousredshift surveys in the GA region have failed to gauge the significanceof the Norma cluster, primarily due to the diminishing effects of theGalactic foreground extinction on the partially obscured galaxies. Inthe absence of the obscuring effects of the Milky Way, the Norma clusterwould have appeared as prominent as the well-known Coma cluster, butnearer in redshift-space. This cluster most likely marks the bottom ofthe potential well of the Great Attractor (Woudt 1998). All the tablesare 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 Very cold dust in galaxiesWe present multi-filter far infrared photometry of active and inactivegalaxies obtained with ISOPHOT. We find that the far infrared andsubmillimeter spectrum of the active galaxies can be described by asingle modified black-body at a color temperature of 31.5 +/- 2.8 K. Theratio of infrared luminosity to gas mass, L_IR/M_gas, where the latterquantity has been obtained from 1.3 mm observations within the central11'' is about 90 L_sun/ M_sun. In contrast, the spectral energydistributions of inactive spirals require, apart from warm dust of 31.8+/- 2.8 K, an additional very cold component of at most 12.9+/- 1.7 K.Determining the gas mass from 1.3 mm dust continuum maps that cover theoptical extent of the inactive spirals we find L_IR/M_gas ~ 3 L_sun/M_sun , a factor ~ 30 lower than for the active galaxies. Based onobservations with ISO, an ESA project with instruments funded by ESAMember States (especially the PI countries: France, Germany, theNetherlands and the United Kingdom) with the participation of ISAS andNASA. Cold dust in galaxies.Not Available ISOPHOT boosts dust masses in spiral galaxiesWe report photometry with ISO between 60 and 200 -um of six galaxies.Three of them are active and the extension of their spectra beyond theIRAS bands up to 200 -um confirms our previous conception that most ofthe dust there is warm and has a fairly uniform temperature of phantom{0}im30K. In the other three galaxies which are inactive, we detect avery cold component (phantom {0}im10K and less) that could hitherto atbest be surmised. The most dramatic consequence is a threefold increasein the mass of interstellar material over what one would calculatewithout the ISO data. Based on observations with ISO, an ESA projectwith instruments funded by ESA Member States (especially the PIcountries: France, Germany, the Netherlands and the United Kingdom) withthe participation of ISAS and NASA. Redshift Distribution of Galaxies in the Southern Milky Way Region 210 degrees < L < 360 degrees and B < 15 degreesAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..107..521V&db_key=AST Dust and CO emission in normal spirals. I. The data.We present 1300μm continuum observations and measurements of the CO(1-0) and (2-1) emission from the inner regions of 98 normal galaxies.The spatial resolution ranges from 11" to 45". The sources come from acomplete FIR selected sample of 138 inactive spirals with an opticaldiameter D_25_<=180". A CO survey of galaxies with the SEST and the 20-m Onsala telescope.A large survey of galaxies in the J=1-0 CO line, performed during1985-1988 using the 15-m SEST and the 20-m millimetre wave telescope ofOnsala Space Observatory, is presented. The HPBW of the telescopes are44" and 33" at 115GHz, respectively. The central positions of 168galaxies were observed and 101 of these were detected in the CO line.More than 20% of these are new detections. Maps of some of the galaxiesare also presented. The Catalog of Southern Ringed GalaxiesThe Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology. The IRAS Bright Galaxy Survey - Part II: Extension to Southern Declinations (delta ~< -30), and Low Galactic Latitudes (f<|b|Complete IRAS Observations and redshifts are reported for all sourcesidentified in the IRAS Bright Galaxy Survey-Part II (hereafter referredto as BGS_2_). Source positions, radial velocities, optical magnitudes,and total flux densities, peak flux densities, and spatial extents at12, 25, and 100 ,microns are reported for 288 sources having 60 micronflux densities > 5.24 Jy, the completeness limit of the originalBright Galaxy Survey [Soifer et al., AJ, 98,766(1989)], hereafterreferred to as BGS_1_. These new data represent the extension of theIRAS Bright Galaxy Survey to southern declinations,δ<~-30^deg^, and low Galactic latitudes,5^deg^<|b|<30^deg^. Although the sky coverage of the BGS_2_ (~19935 deg^2^) is 37% larger than the sky coverage of the BGS_1_, thenumber of sources is 8% smaller due primarily to large scale structurein the local distribution of galaxies. Otherwise, the sources in theBGS_2_ show similar relationships between number counts and flux densityas observed for the 313 sources in the BGS_1_. The BGS_2_ along with theearlier BGS, represents the best sample currently available for definingthe infrared properties of galaxies in the local (z <~ 0.1) Universe. Dust in spiral galaxies, 2We have mapped 32 non-active spirals at 1300 micrometers and measured 7of them at 450 and 800 micrometers. We determine gas masses, dusttemperatures and IR luminosities. From a detailed analysis we find: (1)The spatial extent of the cold dust is comparable to the optical size ofthe galaxies. About 70% of the mass is contained within half the opticalradius; there the gas surface density decreases inversely proportionalto the galactocentric radius. (2) The new submm data set limits on thedecomposition of the FIR spectra into dust components of differenttemperatures. The flux ratios of 450 to 1300 micrometers suggest twokinds of nonactive spirals: those with S450micrometers/S1300 micrometers approximately equal to40, like the Milky Way, where the coldest dust is approximately 20K andaccounts for most of the emission between 100 and 1300 micrometers; onthe other hand, there are galaxies with S450micrometers/S1300 micrometers approximately 20 whichimplies that most of the interstellar dust is extremely cold(approximately 10 K). (3) The ratio of infrared luminosity to gas mass,LIR/Mgas, equals 5 +/- 2 in solar units. Foractive galaxies from the Markarian catalog this ratio is 20 timeslarger. Therefore LIR/Mgas gives a clear signaturefor the activity stage. A search for IRAS galaxies behind the southern Milky WayWe systematically searched for IRAS galaxies with 60 micrometer fluxdensity larger than 0.6 Jy by using the UK Schmidt Infrared and IIIa-JAtlases in the Milky Way region (absolute value of b less than 15 deg)between l = 210 deg and 360 deg. We first selected about 4000 IRAS pointsources by using our far-infrared criteria, which are optimized for thesearch of IRAS galaxies behind the Milky Way region, and then inspectedvisually the optical counterparts of them on the Schmidt Atlas filmcopies. We found 966 IRAS sources associated with galaxy-like objects.The list of the objects is presented here with the IRAS source name,Galactic coordinates, IRAS flux densities, field number and emulsion ofthe Atlas, type and size of galaxy (-like) image, redshift,multiplicity, and cross-identification. Of these, 423 galaxies arealready cataloged in the Catalog of Galaxies and Quasars Observed in theIRAS Survey, and most of the remaining 543 galaxy candidates are newlyidentified in this search. Although the radial velocities are known foronly 387 galaxies, of which 60 were newly measured by us so far, weinferred the contamination by Galactic objects to be small from the goodcorrelation between the sky distributions of the newly identified galaxycandidates and the previously cataloged galaxies. In the regions wherethe Galactic molecular clouds dominate, almost all the sources were notidentified as galaxies. The detected galaxies are clustered in the threeregions around l = 240 deg, 280 deg, and 315 deg, where the projectednumber densities are higher than the whole-sky average of IRAS galaxiesof the same flux limit. General study of group membership. II - Determination of nearby groupsWe 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. IRAS LRS spectroscopy of galaxiesThe study presents IRAS LRS data for 350 galaxies with pointlike IRASsources having either S(12) or S(25) not less than 1.5 Jy. Techniquesare presented which form the mean of an ensemble of LRS spectra, ll ofwhich are only of low signal-to-noise ratio, by quantitative evaluationof the significance of the individual spectra for each object ratherthan mere acceptance of the 'average spectrum' present in the completeLRS data base. Average LRS spectra for groups of galaxies with distinctoptical nuclear properties are formed. Average LRS spectra for severalcategories of objects are presented and interpreted. H II regiongalaxies show the polycyclic aromatic hydrocarbon spectrum of bands inemissions; type 2 Seyferts present a broad emission feature parking near16 microns; LINERs and galaxies without optical emission lines have LRSspectra that decline with wavelength, whereas type 1 Seyferts and WRgalaxies have red spectra suggestive of nonthermal emission processes. The supergalactic plane redshift surveyRedshift measurements, about 1000 of which are new, are presented for1314 galaxies in a survey toward the apex of the large-scale streamingflow for ellipticals. The velocity histogram shows that the excess ingalaxy number counts in this area is due to a substantial concentrationof galaxies with discrete peaks at V about 3000 km/s and V about 4500km/s. After correction for the sampling function, the centroid of thedensity distribution is found to be near V about 4500 km/s.Normalization to the more extensive SSRS survey, which was selected bythe same criteria, shows that the region studied contains a considerableoverdensity of galaxies from 2000 to 6000 km/s. This result is in goodagreement with the 'great attractor' model suggested by Lynden-Bell etal. (1988) which attributes the peculiar motions of elliptical galaxiesover a large region of space to an extensive mass overdensity whichincludes the Hydra-Centaurus and Pavo-Indus superclusters. The centroidof the density enhancement is also consistent with new data by Dresslerand Faber (1990) of peculiar motions of elliptical and spiral galaxies,both of which show a zero crossing of the Hubble line at approximately4500-5000 km/s. A catalogue of Seyfert galaxies.Not Available Southern Galaxy Catalogue.Not Available
Submit a new article