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1.
In order to compare color statistical properties of member galaxies in compact groups with those of field galaxies, we use a compact group (CG) sample which contains 4217 CGs extracted from the MAIN galaxy sample of the SDSS Data Release 4 (SDSS4), and construct a random group sample which has the same distributions of redshift and number of member galaxies as those of the CG sample. It turns out that the mean colors of galaxies in CGs are redder than those of galaxies in random groups. Additionally, we also find that member galaxies in real CGs have a smaller dispersion of colors than those in random groups-at least for g-r, r-i, and i-z colors. Published in Astrofizika, Vol. 50, No. 1, pp. 29–37 (February 2007).  相似文献   

2.
We examine the properties of galaxies in compact groups (CGs) identified in a mock galaxy catalogue based upon the Millennium Run simulation. The overall properties of groups identified in projection are in general agreement with the best available observational constraints. However, only ∼30 per cent of these simulated groups are found to be truly compact in three dimensions, suggesting that interlopers strongly affect our observed understanding of the properties of galaxies in CGs. These simulations predict that genuine CG galaxies are an extremely homogeneous population, confined nearly exclusively to the red sequence: they are best described as 'red and dead' ellipticals. When interlopers are included, the population becomes much more heterogeneous, due to bluer, star-forming, gas-rich, late-type galaxies incorrectly identified as CG members. These models suggest that selection of members by redshift, such that the line-of-sight velocity dispersion of the group is less than 1000 km s−1, significantly reduces contamination to the 30 per cent level. Selection of members by galaxy colour, a technique used frequently for galaxy clusters, is also predicted to dramatically reduce contamination rates for CG studies.  相似文献   

3.
This is a statistical study of galaxies with a UV excess. A sample of 702 Kazarian galaxies (KG) is used. The KGs are identified with objects from the MAPS, IRAS FSC, IRAS PSC, and NVSS catalogs. The O and E magnitudes are known for more than 92% of the KGs. It is shown that the KG sample is complete up to 16m.0 in the blue and to 16m.5 in the red. More than 36% of the KGs are identified with infrared (IR) sources at wavelengths of 12, 25, 60, and 100 m. Calculations of the far IR (FIR) luminosities show that 4% of the KGs are strong FIR emitters (LFIR ≥ 1011 L⊙). More than 32% of the KGs have been identified as radio sources at a frequency of 1.4 GHz. A determination of the radio luminosities shows that the sample of KGs with known radial velocities include one powerful, LR ≥ 1025 W/Hz, radio object (Kaz 273) which is a BL Lac object. A close correlation (r=0.93) is bound between the FIR and radio luminosities for galaxies with a UV excess. An examination of the relationship between the FIR and radio luminosities for galaxies in different spectral classes shows that the correlation coefficient is higher (r=0.99) and the slope of the fit curve is larger (a=1.18) for Seyfert galaxies. Calculations of the logarithm of the ratio of the FIR and radio fluxes indicate that the sample includes 4 KGs with a radio excess, while there are none with an IR excess. __________ Translated from Astrofizika, Vol. 50, No. 3, pp. 369–379 (August 2007).  相似文献   

4.
We present a study focusing on the nature of compact groups (CGs) through the study of their elliptical (E) galaxies. Parameters describing the internal dynamics and the stellar populations of the galaxies are compared with their counterparts in other environments. Our sample has24 bright E galaxies located in the core of Hickson CGs and 11 bright ‘bona fide’ Es, located in the field or very loose groups. Their spectra were obtained with the 2.1 m Telescope at KPNO and have a 4.1 Å resolution over the wavelength range 3500–7000 Å. We have found that, from the dynamical point of view, E galaxies in CGs are essentially similar to those in dense clusters. Moreover, the stellar populations of Es in CGs seem to be older and less metal rich than those in the field, behaviour which has also been observed by Rose et al. (1994).  相似文献   

5.
We use the results of the SCUBA Local Universe Galaxy Survey, a submillimetre (submm) survey of galaxies in the nearby Universe, to investigate the relationship between the far-infrared (FIR)–submm and radio emission of galaxies at both low and high redshift. At low redshift we show that the correlation between radio and FIR emission is much stronger than the correlation between radio and submm emission, which is evidence that massive stars are the source of both the FIR and radio emission. At high redshift we show that the submm sources detected by SCUBA are brighter sources of radio emission than are predicted from the properties of galaxies in the local Universe. We discuss possible reasons for the cosmic evolution of the relationship between radio and FIR emission.  相似文献   

6.
《New Astronomy Reviews》2000,44(4-6):249-256
We are studying star formation effects on the properties of the ISM in low metallicity environments using mid-infrared (MIR) and far-infrared (FIR) observations of starbursting dwarf galaxies taken with the Infrared Space Observatory (ISO) and the Kuiper Airborne Observatory (KAO). Effects of the hard pervasive radiation field on the gas and dust due to the dust-poor environments are apparent in both the dust and gas components. From a 158 μm [CII] survey we find enhanced I[CII]/FIR ratios in dwarf galaxies and I[CII]/I(CO) ratios up to 10 times higher than those for normal metallicity starburst galaxies. We consider MIR observations in understanding the star formation properties of dwarf galaxies and constraints on the stellar SED. Notably, the strong MIR [NeIII]/[NeII] ratios reveal the presence of current massive stellar populations <5 My old in NGC 1569, NGC 1140 and IIZw40. The MIR unidentified infrared bands (UIBs) are weak, if present at all, as a general characteristic in low metallicity environments, revealing the destruction of the smallest carbon particles (e.g. PAHs) over large spatial scales. This is confirmed with our dust modeling: mass fractions of PAHs are almost negligible compared to the larger silicate grains emitting in the FIR as well as the small carbon grains emitting in the MIR, which appear to be the source of the photoelectric gas heating in these galaxies, in view of the [CII] cooling.  相似文献   

7.
We present the largest publicly available catalogue of compact groups (CGs) of galaxies identified using the original selection criteria of Hickson, selected from the Sixth Data Release of the Sloan Digital Sky Survey (SDSS DR6). We identify 2297 CGs down to a limiting magnitude of   r = 18 (∼0.24 groups  deg−2), and 74 791 CGs down to a limiting magnitude of   r = 21 (∼6.7 groups  deg−2). This represents 0.9 per cent of all galaxies in the SDSS DR6 at these magnitude levels. Contamination due to gross photometric errors has been removed from the bright sample of groups, and we estimate it is present in the large sample at the 14 per cent level. Spectroscopic information is available for 4131 galaxies in the bright catalogue (43 per cent completeness), and we find that the median redshift of these groups is   z med= 0.09  . The median line-of-sight (LOS) velocity dispersion within the CGs from the bright catalogue is  σLOS≃ 230 km s−1  , and their typical intergalactic separations are of the order of 50–100 kpc. We show that the fraction of groups with interloping galaxies identified as members is in good agreement with the predictions from our previous study of a mock galaxy catalogue, and we demonstrate how to select CGs such that the interloper fraction is well defined and minimized. This observational data set is ideal for large statistical studies of CGs, the role of environment on galaxy evolution and the effect of galaxy interactions in determining galaxy morphology.  相似文献   

8.
The morphologies of the 96 dwarf (M(B) -17m) galaxies in the Markarian catalog are determined from the digitized Schmidt plates obtained for the construction of the Hubble Space Telescope Guide Star Catalog. The fraction of double nucleus galaxies within the dwarf Markarian galaxies is determined to be twice that found for all galaxies in the Markarian catalog. In addition to the 12 previously known cases, four definite and two probable galaxies with double nuclei are identified. The fraction of dwarf Markarian galaxies with bright star forming regions is found to be twice that of Virgo cluster dwarf galaxies. No Elliptical galaxies are found in the sample. Galaxies with blue compact dwarf and S0 morphologies are more often found to contain unresolved regions of UV excess emission. Dwarf Markarian galaxies with different morphological structures and spectral classes are found to have similar FIR properties.  相似文献   

9.
Together with C+ and CO, C is an important reservoir of carbon in the interstellar medium. We present recent results on the ground state transition of atomic carbon at 492 GHz, and on submillimeter CO lines in nearby galaxies. We show that atomic carbon is a good tracer of molecular gas in spiral galaxy disks. It has also a contribution to the molecular gas cooling: the cooling due to C and CO are of the same order of magnitude, and amounts typically to 4× 10-5 of the FIR continuum. C and CO cooling becomes significant in ULIRG galaxies like Arp220.It is possible to use CI measurements to diagnose the physical conditions in galaxies. Together with CII/CI, the emissivity ratio CI/FIR can be used as a measure of the non-ionizing UV radiation field in galaxies.  相似文献   

10.
To investigate the environmental dependence of u ‐, g ‐, r ‐, i ‐, and z ‐band luminosities, we perform comparative studies of luminosity distributions between galaxy members of compact groups (CGs) and isolated galaxies. It is found that for the r, i, and z bands isolated galaxies have a higher proportion of faint galaxies and a lower proportion of luminous galaxies than galaxy members of CGs, but for the u band an opposite trend is observed. The correlation between the g ‐band luminosity and the environment has different trends in different luminosity regions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

11.
We use host galaxy imaging studies of the PG quasar survey to compare the far-infrared (FIR) properties of quasars with disturbed and undisturbed host galaxies. By using survival analysis, we show that the quasars with disturbed host galaxies, with morphologies classified from a homogeneous data set, have a 60-μm luminosity distribution that is different from that of those with undisturbed hosts with >97 per cent confidence. For morphological classifications using an inhomogeneous data set, including HST data for some objects, this confidence rises to >99 per cent confidence. The mean 60-μm luminosity of the disturbed-host quasars is several times greater than that of the undisturbed-host quasars. However, possible biases in the PG survey might affect these conclusions. Our results are interpreted as supporting the idea that quasars are related to at least some ultraluminous infrared galaxies. We discuss the implications of this result for studies of quasar and galaxy evolution.  相似文献   

12.
We have investigated the radio properties of FIR-luminous galaxies with the VLA (at 1.4, 5, and some at 15.4 GHz), the Cambridge 5-km telescope (at 5 GHz) and the Cambridge Low-Frequency Synthesis Telescope (CLFST at 151 MHz). The existence of a very strong correlation between FIR and radio luminosities has been noted by a large number of authors and is known to extend from dwarf systems to starburst galaxies. However, for some of our sample we find large deviations from the FIR-radio correlation in the sense that these galaxies lie towards the FIR-bright/radio-faint region of the diagram, particularly at 151 MHz. The spectrum of Arp 220 has an unusual low-frequency turnover which we model successfully as a thermally absorbed synchrotron source.  相似文献   

13.
The relationships between the monochromatic luminosity of Seyfert galaxies at frequencies of 0.408, 1.49, and 4.85 GHz and the integrated luminosity in the far infrared (IR) range are investigated. At all radio frequencies they are linear and equally close. Some Seyfert galaxies, of morphological types S0/a, E, and S0, have a far higher radio luminosity than Seyfert spiral galaxies with the same IR luminosity. Most of them are found to have compact central radio components. Seyfert spiral galaxies follow the same relationship between radio and IR emission as non-Seyfert spiral galaxies. The relationships between radio and IR luminosity for the individual groups of galaxies of spectral types Sy 1-Sy 1.5 and Sy 1.8-Sy 2 are also linear.  相似文献   

14.
The dust‐to‐gas ratios in three different samples of luminous, ultraluminous, and hyperluminous infrared galaxies are calculated by modelling their radio to soft X‐ray spectral energy distributions (SED) using composite models which account for the photoionizing radiation from H II regions, starbursts, or AGNs, and for shocks. The models are limited to a set which broadly reproduces the mid‐IR fine structure line ratios of local, IR bright, starburst galaxies. The results show that two types of clouds contribute to the IR emission. Those characterized by low shock velocities and low preshock densities explain the far‐IR dust emission, while those with higher velocities and densities contribute to the mid‐IR dust emission. Clouds with shock velocities of 500 km s–1 prevail in hyperluminous infrared galaxies. An AGN is found in nearly all of the ultraluminous infrared galaxies and in half of the luminous infrared galaxies of the sample. High IR luminosities depend on dust‐to‐gas ratios as high as ∼0.1 by mass, however most hyperluminous IR galaxies show dustto‐gas ratios much lower than those calculated for the luminous and ultraluminous IR galaxies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
We investigate the far-infrared (FIR) properties of a sample of blue compact dwarf galaxies (BCDs) observed by AKARI . By utilizing the data at wavelengths of  λ= 65  , 90 and 140 μm, we find that the FIR colours of the BCDs are located at the natural high-temperature extension of those of the Milky Way and the Magellanic Clouds. This implies that the optical properties of dust in BCDs are similar to those in the Milky Way. Indeed, we explain the FIR colours by assuming the same grain optical properties, which may be appropriate for amorphous dust grains, and the same size distribution as those adopted for the Milky Way dust. Since both interstellar radiation field and dust optical depth affect the dust temperature, it is difficult to distinguish which of these two physical properties is responsible for the change of FIR colours. Then, in order to examine if the dust optical depth plays an important role in determining the dust temperature, we investigate the correlation between FIR colour (dust temperature) and dust-to-gas ratio. We find that the dust temperature tends to be high as the dust-to-gas ratio decreases but that this trend cannot be explained by the effect of dust optical depth. Rather, it indicates a correlation between dust-to-gas ratio and interstellar radiation field. Although the metallicity may also play a role in this correlation, we suggest that the dust optical depth could regulate the star formation activities, which govern the interstellar radiation field. We also mention the importance of submillimetre data in tracing the emission from highly shielded low-temperature dust.  相似文献   

16.
In the last couple of decades hundreds of studies have explored the nature of star‐forming galaxies at different redshifts. This contribution focuses on X‐shooter observations of star‐burst galaxies at 0 < z < 6 from commissioning runs, science verification, and regular observations, and demonstrates the capability of the new instrument in this competitive field. Observations of gravitationally lensed galaxies show that X‐shooter has no limitation in the redshift desert (1.4 < z < 2) where the strong optical emission lines are shifted to the near‐IR region. Physical properties of galaxies, such as masses, metallicities, abundance ratios, and star formation rates can be derived from observations with relatively short integration times for faint galaxies. The simultaneous UV to near‐IR spectral coverage makes derivation of physical quantities more reliable because there are no differential slit losses as may occur when observations from different optical and near‐IR instruments are used. Over the entire redshift range, spectra of faint galaxies will allow us to better measure stellar ages and dominating ionisation sources compared to broad band spectral energy distribution measurements (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
Radio continuum emission at cm wavelengths is relatively little affectedby extinction. When combined with far-infrared (FIR) surveys thisprovides for a convenient and unbiased method to select (radio-loud)AGN and starbursts deeply embedded in gas and dust–rich galaxies. Suchradio-selected FIR samples are useful for detailed investigations ofthe complex relationships between (radio) galaxy and starburst activity, and to determine whether ULIRGs are powered by hidden quasars (monsters) or young stars (babies).We present the results of a large program to obtain identifications andspectra of radio-selected, optically faint IRAS/FSC objects using theFIRST/VLA 20 cm survey (Becker, White and Helfand 1995). These objects are all radio-`quiet' in the sense that their radiopower / FIR luminosities follow the well-known radio/FIR relationshipfor star forming galaxies.We compare these results to a previous study by our group of a sampleof radio-`loud' IRAS/FSC ULIRGs selected from the Texas 365 MHzsurvey (Douglas etal. 1996). Many of these objects alsoshow evidence for dominant, A-type stellar populations, as well as highionization lines usually associated with AGN. These radio-loud ULIRGshave properties intermediate between those of starbursts and quasars,suggesting a possible evolutionary connection.Deep Keck spectroscopic observations of three ULIRGs from these samplesare presented, including high signal-to-noise spectropolarimetry.The polarimetry observations failed to show evidence of a hidden quasar inpolarized (scattered) light in the two systems in which the stellar lightwas dominated by A-type stars. Although observations of a larger samplewould be needed to allow a general conclusion, our current data suggestthat a large fraction of ULIRGs may be powered by luminous starbursts,not by hidden, luminous AGN (quasars).  相似文献   

18.
Until recently far infrared (FIR) observations of galaxies were limited to about a dozen bright and/or active galaxies. New photometric data has become available from Infrared Astronomical Satellite (IRAS) on 33 galaxies (most of them faint) from IRAS Circular Nos. 1, 2, and 3 The FIR spectra of these galaxies are similar. The far infrared fluxF FIR in the wavelength interval 9–118 m of the brighter galaxies is seen to be correlated with the integrated optical magnitudeB T 0 . The 12 and 25 m fluxes of these galaxies exhibit the same dependence onB T 0 as the 10 and 21 m fluxes from Seyferts and other emission-line galaxies. This suggests that the galaxies detected by IRAS are some type of active galaxies in accord with the high percentage of these galaxies predicted by Lock and Rowan-Robinson (1983).  相似文献   

19.
A sample of 2712 radio-luminous galaxies is defined from the second data release of the Sloan Digital Sky Survey (SDSS) by cross-comparing the main spectroscopic galaxy sample with two radio surveys: the National Radio Astronomy Observatories (NRAO) Very Large Array (VLA) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty centimeters (FIRST) survey. The comparison is carried out in a multistage process and makes optimal use of both radio surveys by exploiting the sensitivity of the NVSS to extended and multicomponent radio sources in addition to the high angular resolution of the FIRST images. A radio source sample with 95 per cent completeness and 98.9 per cent reliability is achieved, far better than would be possible for this sample if only one of the surveys was used. The radio source sample is then divided into two classes: radio-loud active galactic nuclei (AGN) and galaxies in which the radio emission is dominated by star formation. The division is based on the location of a galaxy in the plane of 4000-Å break strength versus radio luminosity per unit stellar mass and provides a sample of 2215 radio-loud AGN and 497 star-forming galaxies brighter than 5 mJy at 1.4 GHz. A full catalogue of positions and radio properties is provided for these sources. The local radio luminosity function is then derived both for radio-loud AGN and for star-forming galaxies and is found to be in agreement with previous studies. By using the radio to far-infrared (FIR) correlation, the radio luminosity function of star-forming galaxies is also compared to the luminosity function derived in the FIR. It is found to agree well at high luminosities but less so at lower luminosities, confirming that the linearity of the radio to FIR correlation breaks down below about 1022 W Hz−1 at 1.4 GHz.  相似文献   

20.
The radio and xray properties of spiral galaxies with and without a bar are discussed on the basis of complete samples that we have compiled. The two types of spirals are shown not to differ from one another in emission power in the two indicated ranges. In the case of SB galaxies, the luminosities in the IR, radio, and xray ranges are closely related. The spectral indices of SB and SA galaxies in the 1.4–5 GHz range are the same, on the average. In the case of barred galaxies, however, a definite dependence is observed between the spectral index and both the IR and × ray luminosities, i.e., the spectral index increases as both luminosities increase. It is assumed that this is caused by the bar itself, which stimulates star formation in a barred galaxy. Translated from Astrofizika, Vol. 41. No. 4, pp. 599–608, October–December, 1998.  相似文献   

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