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1.
We show that the number of galaxies with ultraviolet excess in the Kiso catalog decreases rapidly as the inclincation of the galaxy to the line of sight increases. This effect is observed in spiral galaxies of both type Sk and type Sp. Moreover spiral galaxies that are steeply inclined to the line of sight are on the average weaker than galaxies viewed face-on. Due to internal absorption the distribution of UV-excess galaxies over the intensity classes L, M, and H is also distorted.Translated fromAstrofizika, Vol. 37, No. 4, 1994.The authors are grateful to E. G. Nikogosyan for assistance with the computations.  相似文献   

2.
The Second Byurakan Survey (SBS) is a well known combined survey, which uses the presence of UV-excess radiation in the continuum, or the presence of emission-lines in the spectra for the identification of active and star-forming galaxies. This paper reports on a comparative study of 77 galaxies identified with UV-excess, and 34 galaxies identified via emission-line techniques in the fields of the SBS. The spectroscopic parameters used for the comparison are the [OII]3727/H and [OIII]5007/H emission-lines ratios, the equivalent widths of [OII]3727, [OIII]5007 and H emission-lines, and the C [OII]-C H index. Spectroscopic parameters as well as new redshifts were determined from the spectra obtained with the 6m telescope of the Special Astrophysical Observatory (Russia). The main results are: 1) Galaxies discovered via UV-excess technique are preferably more active. 2) Galaxies discovered via emission-line technique are preferably high-excitation low-luminosity star-forming galaxies. 3) UV-excess galaxies with faintest UV-excess radiation are likely candidates to be LINER or Sy2 type objects.  相似文献   

3.
I review the origin of UV-radiation in galaxies of different morphological types. UV-excess in spectra of massive elliptical galaxies which have predominantly old stellar populations is traditionally explained by the contribution of low-mass stars at very late, poorly known stages of evolution—by so called ‘AGB-manqué’ stars or by the population of extended horizontal branch. However recent results from the GALEX survey of a large sample of nearby ellipticals have also demonstrated probable traces of recent star formation in a third of all ellipticals observed. In spiral galaxies extended UV-disks have been discovered by the GALEX; they are certainly illuminated by the current star formation, but what has provoked star formation in the areas of very low gas density, beyond the distribution of older stars, is a puzzle yet. The UV-spectra of starburst galaxies or starforming galactic nuclei are characterized by weak emission lines, if any, quite dissimilar to their optical spectra.  相似文献   

4.
In the galaxy parameter fitting by means of stellar population synthesis, it is found that compared with the evolutionary population synthesis (EPS) model without binary interactions, the stellar age and metallicity of a galaxy derived from the EPS model with binary interactions are larger. But, we are still unclear how the binary interactions affect the galaxy evolution. For the early-type galaxies with the UV-excess phenomenon, there are two main-stream explanations: recent star formation (RSF) and binary interactions. In this study, we obtain the mass return rate and chemical yield for the stellar populations with and without binary interactions. In combination with the galaxy chemical evolution and photoionization models, we study the effects of binary interactions on the chemical evolution and metallicity evolution for the early-type galaxies with the UV-excess phenomenon under the two formation mechanisms. We find that the inclusion of binary interactions can raise the ejected mass, metallicity, alpha element, and accelerate the gas cooling. These can reasonably explain the conclusions made by the EPS models. Moreover, we find that the gas cooling is more efficient under the UV-excess formation mechanism by the binary interactions rather than the RSF, and the ratio of element abundance is different for the two mechanisms, which can be further used to distinguish these two mechanisms.  相似文献   

5.
Photometric intergrated colours (UBVRI+UV selected bands) of elliptical galaxies are theoretically evaluated, accounting for stellar populations of different metal abundance (0.00001Z0.04). The contribution of different evolutionary phases (from M.S. up to Post-A.G.B.) to the integrated fluxes in the various photometric bands is computed. An explanation for the UV-excess in elliptical galaxies and of its dependence on the metallicity (Mg2) and mass is also suggested.  相似文献   

6.
We show that the U-V-color of Markaryan galaxies increases as the inclination of the galaxies increases. We note that the width of the emission lines, UV excess, and inclinations of Markaryan spiral galaxies (in narrow red-shift intervals z=0.004) are interrelated.Translated fromAstrofizika, Vol. 37, No. 3, 1994.  相似文献   

7.
Results from a spectrophotometric study of 21 galaxies with UV excess are presented. The half widths (FWHM) and equivalent widths of observed spectrum lines of these galaxies, as well as the relative intensities of the emission lines observed in the spectrum of the galaxy Kaz243, are determined. It is conjectured that the latter galaxy has the properties of an Sy2 type galaxy. The electron densities and masses of the gaseous components are found for 15 galaxies, along with the masses of 8 galaxies for which the ratio M/L has been calculated. It is shown that the spectral structures of these galaxies do not depend on whether they are members of physical systems or are isolated.  相似文献   

8.
We present the first results of our X‐shooter observations for a sample of dwarf (–17 < MB < –15) galaxies in nearby (0.04 < z < 0.07) galaxy clusters. This luminosity range is fundamental to trace the evolution of higher‐z star‐forming cluster galaxies down to the present day, and to explore the galaxy scaling relations of early‐type galaxies over a broad mass range. Thanks to high resolution and availability of several lines we can derive the velocity dispersion of the galaxies in this range of luminosities and we begin the construction of the fundamental plane of faint early‐type galaxies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

9.
It is well-known that galaxies tend to form elongated associations stretching many degrees across the sky. It is shown here that especially galaxies of about 3000 to 5000 km s-1 redshift define narrow filaments of from 10 to 50° in length. The surprising feature is that galaxies of very bright apparent magnitude tend to occur at the centre or ends of these alignments. The 20 brightest galaxies in apparent magnitude north of °= 0° are investigated here and of the 14 which are uncrowded by nearby bright galaxies, a total of 13 have well marked lines and concentrations of fainter, higher redshift galaxies  相似文献   

10.
E+A galaxies are characterized as galaxies with strong Balmer absorption lines but without any [O  ii ] or Hα emission lines. The existence of strong Balmer absorption lines indicates that E+A galaxies have experienced starburst within the past one gigayear. However, the lack of [O  ii ] and Hα emission lines indicates that E+A galaxies do not have any on-going star formation. Therefore, E+A galaxies are interpreted as post-starburst galaxies. For many years, however, it has been a mystery why E+A galaxies started starburst and why they quenched star formation abruptly. Using one of the largest samples of 266 E+A galaxies carefully selected from the Sloan Digital Sky Survey Data Release 2, we have investigated the environment of E+A galaxies from 50 kpc to 8 Mpc scale, i.e. from a typical distance to satellite galaxies to the scale of large-scale structures. We found that E+A galaxies have an excess of local galaxy density only at a scale of <100 kpc (with a 2σ significance), but not at the cluster scale (∼1.5 Mpc) nor at the scale of large-scale structure (∼8 Mpc). These results indicate that E+A galaxies are not created by the physical mechanisms associated with galaxy clusters or the large-scale structure, but are likely to be created by dynamical interaction with closely accompanying galaxies at a <100 kpc scale. The claim is also supported by the morphology of E+A galaxies. We have found that almost all E+A galaxies have a bright compact core, and that ∼30 per cent of E+A galaxies have dynamically disturbed signatures or tidal tails, which quite strongly suggest the morphological appearance of merger/interaction remnants.  相似文献   

11.
We discuss the detection of redshifted line and continuum emission at radio wavelengths using a Square Kilometer Array (SKA), specifically from low-excitation rotational molecular line transitions of CO and HCN (molecular lines), the recombination radiation from atomic transitions in almost-ionized hydrogen (radio recombination lines; RRLs), OH and H2O maser lines, as well as from synchrotron and free–free continuum radiation and HI 21-cm line radiation. The detection of radio lines with the SKA offers the prospect to determine the redshifts and thus exact luminosities for some of the most distant and optically faint star-forming galaxies and active galactic nuclei, even those galaxies that are either deeply enshrouded in interstellar dust or shining prior to the end of reionization. Moreover, it provides an opportunity to study the astrophysical conditions and resolved morphologies of the most active regions in galaxies during the most active phase of star formation at redshift z 2. A sufficiently powerful and adaptable SKA correlator will enable wide-field three-dimensional redshift surveys at chosen specific high redshifts, and will allow new probes of the evolution of large-scale structure (LSS) in the distribution of galaxies. The detection of molecular line radiation favours pushing the operating frequencies of SKA up to at least 26 GHz, and ideally to 40 GHz, while very high redshift maser emissions requires access to about 100 MHz. To search for LSS the widest possible instantaneous field of view would be advantageous.  相似文献   

12.
Integrated broad-band colors and metallic lines cannot discriminate clearly between the effects of age and Z in old stellar populations. Such data are more sensitive to Z than to age. The Hβ feature provides a way to break this degeneracy. New measurements indicate that the mean stellar ages of typical E galaxy nuclei are fairly young, ranging from 2 to ∼12 Gyr. The outer parts of E galaxies are both older and more metal-poor than nuclei, consistent with the formation of E galaxies via mergers and starbursts. Age effects contribute strongly to the classic color-line strength sequence of E galaxies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
星暴和活动星系核之间的联系是活动星系研究领域最重要、最活跃的研究课题之一。Seyfert星系由于距离较近、数目较多和相对低的核活动,已成为研究星暴和活动星系核之间联系的理想天体。综述了活动星系核中存在星暴的观测证据和Seyflert2型星系核区星暴活动的最新研究结果,着重讨论了存在两类Seyflert2型星系(一类是被遮挡的Seyfert1型星系,另一类是“真正”的Seyfert2型星系即不存在宽线区的Seyfert2型星系)的可能性．通过比较具有和不具有偏振宽线的Seyflert2型星系在红外、射电、光学和X射线光谱性质的差别,发现具有偏振宽线的Seyfert2型星系在本质上和Seyflert1型星系是同一类天体,差别只在于观测者视线方向的不同;而不具有偏振宽线的Seyfert2型星系是一些星系核活动较弱而星暴活动占主导的天体,这些星系从射电、红外、光学到硬X射线,都具有和星暴星系相似的性质。由于这些星系中核的吸积率将比Seyflert1型星系低近两个量级,因而它们很有可能是一些没有宽发射线区的Seyfert2型星系,即所谓的“真正”Seyflert2型星系。  相似文献   

14.
We study the luminosity function and clustering properties of subsamples of local galaxies selected from the Stromlo–APM Survey by the rest-frame equivalent widths of their H α and [O  ii ] emission lines. The b J luminosity function of star-forming galaxies has a significantly steeper faint-end slope than that for quiescent galaxies: the majority of sub- L * galaxies are currently undergoing significant star formation. Emission-line galaxies are less strongly clustered, both amongst themselves and with the general galaxy population, than are quiescent galaxies. Thus as well as being less luminous, star-forming galaxies also inhabit lower density regions of the Universe than quiescent galaxies.  相似文献   

15.
We present the results of a spectral study of 17 galaxies with UV excess from the lists of [1–3]. We determine the equivalent widths of lines, the relative intensities of emission lines for 3 galaxies, the electron densities of the gas components of 9 galaxies, and the gas masses of 2 galaxies. It is shown that the gas component of Galaxy No. 235 has extremely low excitability. In the spectrum of this galaxy the lines [Fell] 4951, 4947 are seen to be distinct, not merging with the line [OIII] 4959. The line H in the spectrum of Galaxy No. 128 has two emission peaks, which seem to have been formed by an absorption component midway between the lines. The line H in the spectrum of Galaxy No. 350 is detected both in emission and absorption, the absorption component lying in the longwave part of the line.Translated fromAstrofizika, Vol. 37, No. 3, 1994.  相似文献   

16.
The perspective given by Iwanowska (inFrom Stars to Quasars, Toru, 1989, volume devoted to Prof. Iwanowska) is developed. The redshifts of the Iwanowska's lines galaxies form five states. We used all the redshifts indicated in the Iwanowska's concept. Our hypotheses can be easily verified in the future checking the new redshifts of galaxies belonging to five lines of galaxies selected by Iwanowska. This solution of the problem of stability of the lines is in serious disagreement with the concept of an anthropic universe advocated by Barrow, Tipler, and Wheeler, nevertheless it fits the view of Grabiska on the problem of antropicity, observation, evaluation of extragalactic data and meta-astronomy, cf. T. GrabiskaRealism and Instrumentalism in Contemporary Physics, Wroclaw Technological Institute, 1992, M. Zabierowski,Status of the Observer in Contemporary Physics, Institute of Physics, 1990.  相似文献   

17.
We have compiled a sample of galaxies whose flux density is higher at 12 microns (f12) than at 25 microns (f25). It is argued thatf12 >f25 effectively selects quiescent galaxies which are less active in infrared, radio, and optical bands than other types of normal galaxies. Moreover galaxies withf12 >f25 do not exhibit the well-known relations that normal galaxies show between far-infrared parameters, for example, the negative correlation betweenf12/f25 andf60/f100. These galaxies also show different far-infrared and radio properties. In our opinion this sample of quiescent galaxies is suitable for use as a control sample when properties of more active galaxies are discussed. It may also be used in modeling galaxies with active star formation or an active nucleus.Translated fromAstrofizika, Vol. 38, No. 3, 1995.  相似文献   

18.
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   

19.
We present a catalog of 520 most isolated nearby galaxies with angular velocities V LG < 3500 km/s, covering the entire sky. This population of “space orphans” makes up 4.8% among 10 900 galaxies with measured radial velocities. We describe the isolation criterion used to select our sample, called the “Local Orphan Galaxies”(LOG), and discuss their basic optical and HI properties. A half of the LOG catalog is occupied by the Sdm, Im and Ir morphological type galaxies without a bulge. The median ratio M gas/M star in the LOG galaxies exceeds 1. The distribution of the catalog galaxies on the sky looks uniform with some signatures of a weak clustering on the scale of about 0.5 Mpc. The LOG galaxies are located in the regions where the mean local density of matter is approximately 50 times lower than the mean global density. We indicate a number of LOG galaxies with distorted structures, which may be the consequence of interaction of isolated galaxies with massive dark objects.  相似文献   

20.
The radial velocities are measured for 45 galaxies located in the neighborhoods of 29 likely isolated galaxies in a new catalog. We find that about 85% of these galaxies actually are well isolated objects. 4% of nearby galaxies with V LG < 3500 km/s are this kind of cosmic "orphan" Translated from Astrofizika, Vol. 52, No. 2, pp. 203–210 (May 2009).  相似文献   

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