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1.
The results of a statistical investigation of bright galaxies with a UV excess are given. The data obtained for them are compared with those for normal galaxies. A list of bright galaxies (mpg ≤14m.5 ) with a UV excess has been compiled, numbering 461. Their absolute stellar magnitudes and average geometrical linear diameters were determined. The relationships between Mpg and log D are given for galaxies with a UV excess and normal galaxies. The graphs of the relationships are expressed by second-degree equations. It is shown that the UV evolutionary stage of the galaxies has no influence on the relationship between Mpg and log D. Translated from Astrofizika, Vol. 43, No. 1, pp. 21-32, January–March, 2000.  相似文献   

2.
The discovery of a flux excess in the far-ultraviolet (FUV) spectrum of elliptical galaxies was a major surprise in 1969. While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes, rather than young stars, their origin has remained a mystery. Here we show that these stars most likely lost their envelopes because of binary interactions, similar to the hot subdwarf population in our own Galaxy. We have developed an evolutionary population synthesis model for the FUV excess of elliptical galaxies based on the binary model developed by Han et al. for the formation of hot subdwarfs in our Galaxy. Despite its simplicity, it successfully reproduces most of the properties of elliptical galaxies with a UV excess: the range of observed UV excesses, both in  (1550 − V )  and  (2000 − V )  , and their evolution with redshift. We also present colour–colour diagrams for use as diagnostic tools in the study of elliptical galaxies. The model has major implications for understanding the evolution of the UV excess and of elliptical galaxies in general. In particular, it implies that the UV excess is not a sign of age, as had been postulated previously, and predicts that it should not be strongly dependent on the metallicity of the population, but exists universally from dwarf ellipticals to giant ellipticals.  相似文献   

3.
Type Ia Supernova (SN Ia) are a powerful, albeit not completely understood, tool for cosmology. Gaps in our understanding of their progenitors and detailed physics can lead to systematic errors in the cosmological distances they measure. We use UV data in two context to help further our understanding of SN Ia progenitors and physics. We analyze a set of nearly 700 light curves, and find no signature of the shock heating of a red giant companion, predicted by Kasen (Astrophys. J. 708:1025, 2010), casting doubt as to frequency of this SN Ia channel. We also use UV imaging of high redshift host galaxies of SN Ia to better understand the environments which SN Ia occur. We show that some high-z elliptical galaxies have current star formation, hindering efforts to use them as low-extinction environments. We show cosmological scatter of SN distances at large effective radii in their hosts is significantly reduced, and argue this is due to the smaller amounts of dust affecting the SN Ia. Finally, we find a two component dependence of SN distance measurements as a function of their host galaxy’s FUV-V color. This indicates that both the age and metallicity/mass of the host galaxy maybe important ingredients in measuring SN Ia distances.  相似文献   

4.
We present William Herschel Telescope spectropolarimetry observations of a complete RA-limited sample of nine low-redshift  (0.05< z <0.2)  3CR radio sources in order to investigate the nature of the ultraviolet (UV) excess in nearby powerful radio galaxies. Of the nine galaxies studied in detail from this sample, we find that four show a measurable UV excess following nebular continuum subtraction, but none of the sources shows significant polarization in the UV. One of the radio galaxies with a UV excess – 3C 184.1 – shows evidence for broad permitted lines and hence direct active galactic nucleus (AGN) light. In the remaining three galaxies we argue that the most likely contributor to the UV excess is a young stellar component. For these three galaxies we find that the best-fitting model for the optical/UV continuum consists of a combination of an old stellar population  (10–15 Gyr  old elliptical galaxy) plus a reddened young stellar population  (0.05–2 Gyr)  . The reddened young stellar component typically accounts for half of the total flux at 4780 Å, following nebular continuum subtraction, and   E ( B - V )  values of between 0.2 and 0.7 mag are required. However, for the majority of sources in our sample (six out of nine), continuum modelling provides no evidence for a significant young stellar component in the nuclear regions of the host galaxies. Our results are discussed in the context of far-infrared evidence for star formation activity.  相似文献   

5.
We aim to understand the properties at the locations of supernova(SN) explosions in their host galaxies and compare with the global properties of these host galaxies. We use the integral field spectrograph(IFS) of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA) to generate 2 D maps of the parameter properties for 11 SN host galaxies. The sample galaxies are analyzed one by one in detail in terms of their properties of velocity field, star formation rate, oxygen abundance, stellar mass, etc.This sample of SN host galaxies has redshifts around z~0.03, which is higher than those of previous related works. The higher redshift distribution allows us to obtain the properties of more distant SN host galaxies. Metallicity(gas-phase oxygen abundance) estimated from integrated spectra can represent the local metallicity at SN explosion sites with small bias. All the host galaxies in our sample are metal-rich galaxies(12+log(O/H) 8.5) except for NGC 6387, which means SNe may be more inclined to explode in metallicity-rich galaxies. There is a positive relation between global gas-phase oxygen abundance and the stellar mass of host galaxies. We also try to compare the differences of the host galaxies between SNe Ia and SNe II. In our sample, both SNe Ia and SNe II can explode in normal galaxies, but SNe II can also explode in an interacting or a merging system, in which star formation is occurring in the galaxy.  相似文献   

6.
A list is presented of 122 new galaxies with UV excess observed on plates obtained using the 40″ Schmidt telescope at the Byurakan Observatory with a 1°.5 objective prism. It is shown that the relative number of galaxies with a strong UV excess (classes 1 and 2) listed in Table 1 is roughly 55.7%. This is 6.7% higher than for the previously observed galaxies. These samples also differ in terms of the morphology of the spectra. The largest deviation, approximately 9.9%, occurs for type “sd.”__________Published in Astrofizika, Vol. 48, No. 3, pp. 393–408 (August 2005).  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 an ongoing spectroscopic survey of galaxies selected in the rest frame ultraviolet (UV). The source catalogue has been constructed from a flux-limited sample of stars, galaxies and QSOs imaged at 2000 Å in Selected Area 57 with the FOCA balloon-borne imaging camera. Accurate positions for the UV sources have been obtained by matching with optical counterparts using APM scans of the Palomar Sky Survey limited at B   20.5. Here we present results derived from optical spectroscopy conducted with the WIYN telescope and the WHT for 142 faint sources. The redshift distribution for this UV-selected sample extends over 0 <  z  < 0.5, and a high fraction of the sources show intense nebular emission lines and UV–optical colours bluer than normal Hubble sequence galaxies. Such UV-selected surveys are thus a very efficient way to locate and study intermediate-redshift galaxies undergoing intense star formation. Although our sample is currently small, we derive a rest frame UV luminosity function with a steep faint-end slope consistent with that found for late-type galaxies in optical samples. However, the integrated luminosity density derived implies a volume-averaged star formation rate higher than other recent estimates, assuming a normal initial mass function. If representative of other UV fields, as suggested by UV number count studies, our data imply that the local abundance of star-forming galaxies may have been underestimated, and consequently claims for strong evolution in the global star formation rate in the range 0 <  z  < 1 overstated. An intensive study of a large UV-selected sample is likely to reveal important information on the declining population of star-forming galaxies of all types.  相似文献   

9.
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   

10.
The characteristics of the starburst galaxies from the Pico dos Dias survey (PDS) are compared with those of the nearby ultraviolet (UV) bright Markarian starburst galaxies, having the same limit in redshift ( v h < 7500 km s−1) and absolute B magnitude ( MB < −18). An important difference is found: the Markarian galaxies are generally undetected at 12 and 25 μm in IRAS . This is consistent with the UV excess shown by these galaxies and suggests that the youngest star-forming regions dominating these galaxies are relatively free of dust.
The far-infrared selection criteria for the PDS are shown to introduce a strong bias towards massive (luminous) and large size late-type spiral galaxies. This is contrary to the Markarian galaxies, which are found to be remarkably rich in smaller size early-type galaxies. These results suggest that only late-type spirals with a large and massive disc are strong emitters at 12 and 25 μm in IRAS in the nearby Universe.
The Markarian and PDS starburst galaxies are shown to share the same environment. This rules out an explanation of the differences observed in terms of external parameters. These differences may be explained by assuming two different levels of evolution, the Markarian being less evolved than the PDS galaxies. This interpretation is fully consistent with the disc formation hypothesis proposed by Coziol et al. to explain the special properties of the Markarian SBNG.  相似文献   

11.
We investigate the history of galactic feedback and chemical enrichment within a sample of 15 X-ray bright groups of galaxies, on the basis of the inferred Fe and Si distributions in the hot gas and the associated metal masses produced by core-collapse and Type Ia supernovae (SNe). Most of these cool-core groups show a central Fe and Si excess, which can be explained by prolonged enrichment by SN Ia and stellar winds in the central early-type galaxy alone, but with tentative evidence for additional processes contributing to core enrichment in hotter groups. Inferred metal mass-to-light ratios inside r 500 show a positive correlation with total group mass but are generally significantly lower than in clusters, due to a combination of lower global intracluster medium (ICM) abundances and gas-to-light ratios in groups. This metal deficiency is present for products from both SN Ia and SN II, and suggests that metals were either synthesized, released from galaxies or retained within the ICM less efficiently in lower mass systems. We explore possible causes, including variations in galaxy formation and metal release efficiency, cooling out of metals, and gas and metal loss via active galactic nuclei (AGN) – or starburst-driven galactic winds from groups or their precursor filaments. Loss of enriched material from filaments coupled with post-collapse AGN feedback emerges as viable explanations, but we also find evidence for metals to have been released less efficiently from galaxies in cooler groups and for the ICM in these to appear chemically less evolved, possibly reflecting more extended star formation histories in less massive systems. Some implications for the hierarchical growth of clusters from groups are briefly discussed.  相似文献   

12.
The relevance of interaction to the presence of Seyfert or starburst activity in the nuclei of galaxies is examined. We focus the attention on the close environments of spectroscopically selected samples of Seyfert-1, Seyfert-2 and starburst galaxies. In particular the results of a statistical procedure aimed at finding physical pairs are tested with redshift measurements of the identified pairs. Seyfert and starburts galaxies show an excess of physical companions compared to normal galaxies. This excess tends to increase as one moves from Seyfert to starburst galaxies.  相似文献   

13.
The quest for the cosmological parameters has come to fruition with the identification of a number of supernovae at a redshift of     . Analyses of the brightness of these standard candles reveal that the Universe is dominated by a large cosmological constant. The recent identification of the     SN 1997ff in the northern Hubble Deep Field has provided further evidence for this cosmology. Here we examine the case for gravitational lensing of SN 1997ff owing to the presence of galaxies lying along our line of sight. We find that, while the alignment of SN 1997ff with foreground masses is not favourable for it to be multiply imaged and strongly magnified, two galaxies do lie close enough to result in significant magnification:     for the case where these elliptical galaxies have a velocity dispersion of 200 km s−1. Given the small difference between supernova brightnesses in different cosmologies, detailed modelling of the gravitational lensing properties of the intervening matter is therefore required before the true cosmological significance of SN 1997ff can be deduced.  相似文献   

14.
In order to investigate the influence of environment on supernova (SN) production, we have performed a statistical investigation of the SNe discovered in isolated galaxies, in pairs and in groups of galaxies. 22 SNe in 18 isolated galaxies, 48 SNe in 40 galaxy members of 37 pairs and 211 SNe in 170 galaxy members of 116 groups have been selected and studied.
We found that the radial distributions of core-collapse SNe in galaxies located in different environments are similar, and consistent with those reported by Bartunov, Makarova & Tsvetkov . SNe discovered in pairs do not favour a particular direction with respect to the companion galaxy. Also, the azimuthal distributions inside the host members of galaxy groups are consistent with being isotropics. The fact that SNe are more frequent in the brighter components of the pairs and groups is expected from the dependence of the SN rates on the galaxy luminosity.
There is an indication that the SN rate is higher in galaxy pairs compared with that in groups. This can be related to the enhanced star formation rate in strongly interacting systems.
It is concluded that, with the possible exception of strongly interacting systems, the parent galaxy environment has no direct influence on SN production.  相似文献   

15.
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   

16.
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   

17.
We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The statistical study of SN hosts shows that there is no significant difference between morphologies of hosts in our sample and the larger general sample of SN hosts in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of host and neighbor galaxies in pairs. The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair.  相似文献   

18.
The Tully–Fisher Relationship (TFR) is utilized to identify anomalous redshifts in normal spiral galaxies. Three redshift anomalies are identified in this analysis: (1) several clusters of galaxies are examined, in which late type spirals have significant excess redshifts relative to early-type spirals in the same clusters; (2) galaxies of morphology similar to ScI galaxies are found to have a systematic excess redshift relative to the redshifts expected if the Hubble Constant is 72 km s−1 Mpc−1; (3) individual galaxies, pairs, and groups are identified which strongly deviate from the predictions of a smooth Hubble flow. These redshift deviations are significantly larger than can be explained by peculiar motions and TFR errors. It is concluded that the redshift anomalies identified in this analysis are consistent with previous claims for large non-cosmological (intrinsic) redshifts.  相似文献   

19.
It is argued that all SNI come from short-lived stars and do not occur in a typical, isolationist, gas-free early-type galaxy. SNI occur only in those galaxies which accrete gas and form stars. SN properties of E/SOs are, therefore, determined by environmental factors. Presence of gas and dust in early-type galaxies, SN occurrence, nuclear emission, and radio-activity are all manifestations of the same phenomenon, namely availability of gas.What is now urgently required is multi-colour photometry of supernovic early-type galaxies around the regions of recorded SN to see if there are signs of recent star-formation.  相似文献   

20.
We present the results of the population synthesis of the population ofthe supernovae progenitors. Both single and double degenerate progenitorsof SN Ia are considered. We compute the cosmic rate histories for SN I,SN II and both classes of SN Ia, and present them in the form of redshiftand magnitude distributions. These results can be compared with observationaldata, allowing to estimate the star formation rate history and thecosmological parameters including ωbaryons which cannot beestimated from analysing the Hubble diagrams of supernovae.We find that single degenerate (SD) SN Ia are younger than double degenerate (DD) ones, and so the SN Ia in elliptical galaxies should be mostly DD.We propose to use the redshift dependence of relative supernovae rates indifferent types of galaxies, or of different supernovae types forinterpretation of observations. These relative rates should be lessinfluenced by the selection effects than the absolute ones. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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