내용
사진
사진 업로드
DSS Images Other Images
관련 글
Radio emission from AGN detected by the VLA FIRST survey
Using the most recent (April 2003) version of the VLA FIRST survey radiocatalog, we have searched for radio emission from >2800 AGN takenfrom the most recent (2001) version of the Veron-Cetty and Veron AGNcatalog. These AGN lie in the 9033 square degrees of sky alreadycovered by the VLA FIRST survey. Our work has resulted in positivedetection of radio emission from 775 AGN of which 214 are new detectionsat radio wavelengths.Tables 3 and 4 are only available in electronic form 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/416/35
| 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
| The FIR-radio correlation of Wolf-Rayet galaxies and the role of star formation in LINERs
We find that a preliminary classification of LINERs' energetics may bemade in terms of the FIR-radio correlation of Wolf-Rayet galaxies. TheAGN- or starburst-supported LINERs can be distinguished by theirFIR-to-radio ratio, Qequiv L(1.4GHz)/ L(60mum )> or <0.01. It isinteresting to note that almost all the LINERs with inner rings might bestarburst-supported, indicating reduced AGN activities compared withthose of the AGN-supported ones. We also find that a shock-heating phasefor the warm dust component might be important for some starbursts atthe burst age of >= 107 yr, with Q<0.001.
| The role of star formation in liners.
Not Available
| Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
| Galaxy Properties at the North Galactic Pole. I. Photometric Properties on Large Spatial Scales
A two-color study of the galaxies detected on POSS-I in a 289 squaredegree region centered on the North Galactic Pole is presented. We use avariety of mapping techniques to characterize the large-scale spatialdistribution of galaxies. The depth and sample size of this new surveyallows, for the first time, the isolation of large photometricsubsamples of galaxies in high- and low-density environments on thescale of superclusters. Our principal finding is a statisticallysignificant difference between the mean photometric properties of thesesubsamples in the sense that galaxies in the high-density Coma andfilament environments have redder colors and larger concentrationindices than galaxies drawn from low-density interfilament regions.These results are in accord with the known morphology-density relation.Thus, appropriately chosen photometric and morphological parameters, inconcert with a galaxy surface density map, can be used to selectstructures from the projected galaxy distribution which correspond toregions of high density. An illustration of this point is our discoveryof a concentration of blue galaxies identified in our maps near the coreof the Coma cluster. This feature is comprised of early-type galaxieswhich exhibit signs of current or recent star formation. These resultsare predicated on relations between morphological type and photometricparameters derived from APS scans of POSS-I. We therefore discuss theimage calibration procedures used to compile our catalog of physicallysignificant photometric parameters. We demonstrate the morphologicaltype dependence among quantities such as mean color and imageconcentration index, and the lack of such a dependence for mean surfacebrightness.
| CO, HI and cold dust in a sample of IRAS galaxies.
Using the IRAM 30m, SEST 15m, and Nancay radiotelescopes, we havegathered the 1mm continuum emission, the intensities of the J=1-0 lineof the CO molecule and of the atomic hydrogen line at 21cm for twosamples of IRAS galaxies. The southern sample was selected from the IRASCatalogue and is complete at the limiting flux of 2Jy at 60μm; of the10 northern objects 7 belong to the Smith et al. complete sample (1987)and 3 are isolated objects. Using these data, we have estimated theatomic hydrogen masses from the 21cm emission, the molecular gas massesfrom the CO(1-0)line brightness, and the dust and gas masses from the mmcontinuum emission using two "extreme" dust models. The main conclusionsof this work for far-infrared selected galaxies can be summarized in thefollowing points: (1) the median value of M_H_2__/M_HI_ is 0.5, meaningthat the atomic phase dominates in these galaxies. The fraction of gasin molecular form increases with increasing FIR luminosity but does notshow any obvious trend with other galaxy properties, in particular withthe FIR surface brightness. (2) the H_2_ surface density derived fromCO(1-0)emission is better correlated with the cold dust surface densitythan the HI surface density, but the correlation of HI with dust is notnegligible (we found a correlation coefficient of 0.5, while thecorrelation coefficient with σ_H_2__ is 0.70). Thus, globally inthese galaxies, the cold dust emission is likely associated with boththe molecular and atomic phases. Indeed, the dust surface density isalso correlated with the total gas surface density. (3) the FIR surfacebrightness increases as the third power of the S(60μm) /S(100μm)ratio. It shows a tight correlation with both the H_2_ and dust surfacedensities and a weaker one with the HI surface density. This suggeststhat a large part of the far-infrared emission of these galaxiesoriginates in the molecular medium. (4) the gas-to-dust ratio, (M_H_2__+M_HI_)/M_d_ ranges between 100 and 1000 and its average value is 230,close to the Galactic value. There is indeed a clear trend: this ratiodecreases as the FIR surface density increases. This result can beexplained in the framework of an enhancement of metallicity in galaxydiscs having a higher star formation rate.
| 1.2-mm continuum observations of IRAS galaxies : implications for gas mass and cold dust component.
Not Available
| High-luminosity IRAS galaxies. II - Optical spectroscopy, modelling of starburst regions and comparison with structure
Moderate-resolution spectrophotometry was used to obtain variousemission-line ratios and emission-line luminosities for a completesample of predominantly high-luminosity IRAS galaxies. Most of theobjects exhibit H II region-like spectra, while about 12 percent areSeyferts or LINERs. The results show the IRAS galaxies to be of lowerionization than an optically selected sample of H II region-likegalaxies, possibly due to either high metallicities or to their highdust content. Although the estimated number of O stars present isconsistent with the observed emission-line flux, the IR to emission-lineluminosity ratio of all the IRAS galaxies is very high. The presentobservations can be reconciled using a model with two types of regions,type I clouds (with extinctions of about 20) representing very recentstar formation, and type II clouds (with extinctions of about 1)representing older starburst and/or general disk star formation.
| High-luminosity IRAS galaxies. I - The proportion of IRAS galaxies in interacting systems
An analysis of CCD images of a sample of 60 high-luminosity IRASgalaxies from the redshift survey of Lawrence et al. (1986) and of acontrol sample of 87 optically selected galaxies from the Durhamredshift survey (Peterson et al., 1986) is presented. It is found that18 + or - 5 percent of the optically selected galaxies are interactingor merging systems, and that 11 + or - 8 percent of the low-luminosityIRAS galaxies are interacting or merging. At high luminosities, theproportion is shown to be 46 + or - 12 percent. The results suggest thatalthough galaxy interaction is a common causal factor in luminous IRactivity, it is far from being the ubiquitous factor suggested in recentreports.
| The Wasilewski sample of emission-line galaxies - Follow-up CCD imaging and spectroscopic and IRAS observations
The results of an extensive imaging and spectroscopic follow-up of theobjective prism-selected emission line galaxy (ELG) sample of Wasilewski(1982) are presented. Fluxes at 12, 25, 60, and 100 microns were alsoobtained from the coadded IRAS survey data. ELGs found by objectiveprism surveys are found to be generally small and underluminous galaxieswhich usually have higher than average optical surface brightness. TheSeyfert detection rate in objective prism surveys is roughly 10 percentand the ratio of the space densities of Seyfert 2 to Seyfert 1 galaxiesis significantly larger than unity. Most of the galaxies selected byobjective prism surveys are star-forming, late-type spirals which oftenshow disturbed morphology. About 25 percent of the galaxies detected bythe surveys are faint, high-excitation metal-poor compact H II regions.
| A model for far-IR emission of non-Seyfert Markarian galaxies
The paper presents simple models for the FIR emission from extended H IIregions and from cooler dust heated by the general interstellarradiation field. The models account for a realistic grain-sizedistribution including PAH molecules. In addition, the model explainsthe observed correlation between the FIR to optical luminosity ratio andthe 60-10 micron colors.
| Studies of IRAS sources at high galactic latitudes. IV - New redshifts and the spectroscopic properties of IRAS galaxies
New redshifts, H-alpha line fluxes, and optical continuum fluxes forIRAS galaxies are presented. Most of the galaxies show emission linesstronger than those found in optically selected spiral galaxies andcharacteristic of normal H II regions, suggesting a burst of starformation as the basic energy source. There is considerable reddeningtoward the emission-line regions and toward the unobserved UV sources,most of the energy emerging in the infrared. A minority of the casesshow high-excitation emission lines, and these are also distinguished bytheir infrared colors, typical luminosities, and emission-linestrengths. Type 2 Seyferts outnumber type 1s by two to one.
| A study of a flux-limited sample of IRAS galaxies
Redshift data and accurate four-color infrared photometry are presentedfor a complete IRAS sample of galaxies brighter than 2 Jy at 60 microns.A simple power law provides a good fit to the distribution forluminosities from 10 to the 10th to 10 to the 12th solar. There is noindication of an exponential dropoff in the luminosity function at highenergies. A flattening of the luminosity function occurs at L less than10 to the 20th solar. The highest luminosity galaxies typically arefound in multiple, possibly interacting, systems and exhibit marginallynarrower infrared spectral energy distributions than the isolatedspirals which predominate at low luminosities. Infrared-bright galaxiescome from a different population than the majority of optically brightgalaxies. In particular, galaxies of low blue luminosity are not stronginfrared emitters.
| Radio identifications of IRAS point sources with B greater than 30 deg
The present radio identifications of IRAS point sources on the basis ofGreen Bank 1400 MHz survey maps notes that 365 'hot' IR sources are notdetectable radio sources, and that nearly all 'cool' high latitude IRASsources are extragalactic. The fainter IR-source identificationsencompass optically bright quasars, BL Lac objects, Seyfert galaxies,and elliptical galaxies. No IRAS sources could be identified withdistant elliptical radio galaxies, so that although the radio and IRfluxes of most IRAS extragalactic sources are tightly correlated,complete samples of strong radio and IR sources are almost completelydisjoint; no more than 1 percent of the IR sources are radio sources andless than 1 percent of the radio sources are IR ones.
| The space density and spectroscopic properties of a new sample of emission-line galaxies
A 4-deg objective prism survey for low redshift emission line galaxiesconducted over an 825 sq deg region of the sky indicates that a newsample of emission line galaxies is available even in areas which havebeen well searched with the 'excess UV-continuum' technique. Thesegalaxies commonly occur in systems with peculiar morphology, indicatinggravitational interaction with a close companion or other disturbance.The space density of the new galaxies is found to be similar to thespace density of the Markarian galaxies. The present galaxies representabout 8 percent of all nearby galaxies in the -16.5 to -22.5 absolutemagnitude range, and are composed of a population which is completelyindependent of the Markarian sample.
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
