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1.
From published data on X-ray sources identified with clusters of galaxies the X-ray luminosity function of the clusters was derived to ϕx ˜ Lx-0.8 in the range 1043 ≦ Lx ≦ (2–3) · 1045 ergs/s. For Lx > 3 · 1045 ergs/s the function decreases abruptly.  相似文献   

2.
We present an analysis of BV R c I c observations of the field sized around 4′ × 4′ centered at the host galaxy of the gamma-ray burst GRB021004 with the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We measured the magnitudes and constructed the color diagrams for 311 galaxies detected in the field (S/N>3). The differential and integral counts of galaxies up to the limit, corresponding to 28.5 (B), 28.0 (V), 27.0 (R c ), 26.5 (I c ) were computed. We compiled the galaxy catalog, consisting of 183 objects, for which the photometric redshifts up to the limiting magnitudes 26.0 (B), 25.5 (V), 25.0 (R c ), 24.5 (I c ) were determined using the HyperZ code. We then examined the radial distribution of galaxies based on the z estimates. We have built the curves expected in the case of a uniform distribution of galaxies in space, and obtained the estimates for the size and contrast of the possible super-large-scale structures, which are accessible with the observations of this type.  相似文献   

3.
The results of morphological and colorimetrical investigation of several Markarian galaxies are presented. In most cases the nuclei of galaxies have U–B and B–V smaller than the integral values of the galaxies. By the colours of its nucleus Markarian 185 must be a normal galaxy. 55% of the galaxies in the sample are spirals of both types.  相似文献   

4.
We have identified 22 galaxies with photometric redshifts zph=5–7 in the northern and southern Hubble Space Telescope deep fields. An analysis of the images of these objects shows that they are asymmetric and very compact (～1 kpc) structures with high surface brightness and absolute magnitudes of MB≈?20m. The average spectral energy distribution for these galaxies agrees with the distributions for galaxies with active star formation. The star formation rate in galaxies with zph=5–7 was estimated from their luminosity at λ=1500 Å to be ~30 M⊙yr?1. The spatial density of these objects is close to the current spatial density of bright galaxies. All the above properties of the distant galaxies considered are very similar to those of the so-called Lyman break galaxies (LBGs) with z ～ 3–4. The similarity between the objects considered and LBGs suggests that at z ～6, we observe the progenitors of present-day galaxies that form duringmergers of protogalactic objects and that undergo intense starbursts.  相似文献   

5.
Data from the H I Parkes All-Sky Survey (HIPASS) of the southern sky in the neutral hydrogen line are used to determine the radial velocities and widths of the H I line for flat spiral galaxies of the Revised Flat-Galaxy Catalog (RFGC) seen edge-on. The sample of 103 flat galaxies detected in HIPASS is characterized by a median radial velocity of +2037 km/sec and a median width of the H I line at the level of 50% of maximum of 242 km/sec. For RFGC galaxies the 50% detection level in HIPASS corresponds to an apparent magnitude B t = 14 m .5 or an angular diameter a = 2.9. The relative number of detected galaxies increases from 2% for the morphological types Sbc and Sc to 41% for the type Sm. The median value of the ratio of hydrogen mass to total mass for RFGC galaxies is 0.079. With allowance for the average internal extinction for edge-on galaxies, <B t< = 0 m .75, the median ratio of hydrogen mass to luminosity, M H I/L B = 0.74 M /L , is typical for late-type spirals. Because of its small depth, HIPASS reveals only a few RFGC galaxies with previously unknown velocities and line widths.  相似文献   

6.
In the framework of study of the evolutionary status of galaxies in the nearby Lynx-Cancer void, we present the results of the SAO RAS 6-m telescope spectroscopy for 20 objects in this region. The principal faint line [Oiii]λ4363 Å, used to determine the electron temperature and oxygen abundance (O/H) by the classicalmethod, is clearly detected in only about 2/3 of the studied objects. For the remaining galaxies this line is either faint or undetected. To obtain the oxygen abundances in these galaxies we as well apply the semi-empirical method by Izotov and Thuan, and/or the empirical methods of Pilyugin et al., which are only employing the intensities of sufficiently strong lines. We also present our O/H measurements for 22 Lynx-Cancer void galaxies, for which the suitable Sloan Digital Sky Survey (SDSS) spectra are available. In total, we present the combined O/H data for 48 Lynx-Cancer void galaxies, including the data adopted from the literature and our own earlier results. We make a comparison of their locations on the (O/H)-MB diagram with those of the dwarf galaxies of the Local Volume in the regions with denser environment. We infer that the majority of galaxies from this void on the average reveal an about 30% lower metallicity. In addition, a substantial fraction (not less than 10%) of the void dwarf galaxies have a much larger O/H deficiency (up to a factor of 5). Most of them belong to the tiny group of objects with the gas metallicity Z ⊙/20 or 12+log(O/H)?7.35. The surface density of very metal-poor galaxies (Z ⊙/10) in this region of the sky is 2–2.5 times higher than that, derived from the emission-line galaxy samples in the Hamburg-SAO and the SDSS surveys. We discuss possible implications of these results for the galaxy evolution models.  相似文献   

7.
We used the Revised Flat Galaxy Catalog (RFGC) to create a sample of ultra-flat galaxies (UFG) covering the whole northern and southern sky apart from theMilkyWay zone. It contains 817 spiral galaxies seen edge-on, selected into theUFG sample according to their apparent axial ratios (a/b)B ≥ 10.0 and (a/b)R ≥ 8.53 in the blue and red bands, respectively. Within this basic sample we fixed an exemplary sample of 441 UFG galaxies having the radial velocities of VLG < 10000 km s?1, Galactic latitude of | b |> 10° and the blue angular diameter of aB > 1.′0. According to the Schmidt test the exemplary sample of 441 galaxies is characterized by about (80–90)% completeness, what is quite enough to study different properties of the ultra-flat galaxies. We found that more than 3/4 of UFGs have the morphological types within the narrow range of T = 7± 1, i.e. the thinnest stellar disks occur among the Scd, Sd, and Sdm types. The average surface brightness of UFG galaxies tends to diminish towards the flattest bulge-less galaxies. Regularly shaped disks without signs of asymmetrymake up about 2/3 both among all the RFGC galaxies, and the UFG sample objects. About 60% of ultra-flat galaxies can be referred to dynamically isolated objects, while 30% of them probably belong to the scattered associations (filaments, walls), and only about 10% of them are dynamically dominating galaxies with respect to their neighbours.  相似文献   

8.
A statistical study of the dependence of the star formation rate in the nuclear regions of 39 Kazarian galaxies on the integral parameters of these galaxies is carried out on the basis of spectra from SDSS DR6. The value of SFR/kpc2 for our sample lies in the range 0.013÷2.04M ⨀ year−1kpc−2 (with the maximum value of 2.04 corresponding to the Kaz 98 (merger)). It is found that the surface density of the rate of star formation correlates positively with the bar structure parameter and EW(Hα), and that, for spiral galaxies of early morphological types, SFR/kpc2 is greater than for the later types. It is shown that the color B-R for the galaxies and the color (u − g) nucl for the nuclear region correlate positively with the total absorption A(Hα) in the Ha line for the nuclear region. The average value of A(Hα) for our samples is found to be A(Hα)=1.3±0.09 magnitudes. Translated from Astrofizika, Vol. 52, No. 2, pp. 211–224 (May 2009).  相似文献   

9.
We present the results of our observational study of two candidates for polar-ring galaxies (PRGs). Both objects, A2330-3751 and SDSS J000911.57-003654.7, are giant edge-on galaxies with large-scale structures resembling polar rings observed along their minor axes. The optical diameter of the putative ring reaches 60 kpc in A2330-3751 and 18 kpc in SDSS J000911.57-003654.7. To estimate the space density of PRGs, we have constructed their luminosity function in the range of B-band absolute magnitudes from −17· m 5 to −21· m 5. We have found that ∼10−3 of the nearby galaxies exhibit polar structures. Polar rings around early-type (E/S0) galaxies are encountered approximately a factor of 3 more frequently than those around spiral ones. According to our estimates, ∼20–30 PRGs in which large-scale rings are seen almost face-on must be observed among relatively bright galaxies (B ≤ 15 m ).  相似文献   

10.
We present spectroscopically confirmed quasars in the 25 sq. degrees A1-field to a limiting magnitude of mB = 18.0. Our estimate of the quasar density of 0.28 ± 0.11 objects per sq. degree based on the “complete” sample of A1-qusars is in agreement with the observed integral number-magnitude relation. However, we consider this value as still a lower limit of the quasar density in the A1-field due to the uncertainties during the colour based selection of objects, especially their brightness dependence, resulting in serious selection effects. Thus, the quasar density of the A1 survey may be underestimated up to 30% and does not contradict the recently estimated incompletness of the BQS survey.  相似文献   

11.
To investigate the relationship between solar activity and the large-scale axisymmetric magnetic field of the Sun, we inferred from sunspot data over the period 1964–1985 a latitude–time distribution of magnetic field associated with active regions. This has been done allowing for both bipolar structure of the active regions and inclination of their axes to parallels of latitude, so the inferred magnetic field characterizes latitudinal separation of magnetic polarities which might be related to the large-scale magnetic field of the Sun according to the Babcock–Leighton model. The inferred magnetic field, A z, is compared with the longitude-averaged (zonal) magnetic field of the Sun, B z, derived from series of magnetograms obtained at Mount Wilson Observatory in the years 1964–1976, and at Kitt Peak National Observatory during the period from 1976 to 1985. The inferred magnetic field, A z, exhibits a complex structure distribution of magnetic polarities with respect to latitude and time. Apart from concentration of the different polarity magnetic fields inside the high- and low-latitude portions of the sunspot belts, bipolar active regions produce an intensive, shorter-scale component of the magnetic field which varies on the time scale of about 2 years. Such a short-term variation of A z reveals substantial correlation with the short-term component of B z which has the form of the poleward-drifting streams of magnetic field. Most significant correlation takes place between the short-term variations of A z occurring at latitudes below 20° and those of the large-scale magnetic fields occurring at middle latitudes of 40–50°. Moreover we analyze harmonic coefficients a l and b l obtained by expanding A z and B z into series in terms of the spherical harmonics. Power spectra of the time-dependent harmonic coefficients indicate that both A z and B z reveal a number of resonant modes which oscillate either with the 22-year period in the case of the anti-symmetric (odd-l) modes or with periods of about 2 years in the case of the symmetric (even-l) modes, but the resonant modes of A z have significantly larger values of the spherical harmonic degree l (and, hence, smaller spatial scales) as compared to those of B z. It is found that there is a close relationship between the harmonic coefficients b l and a m for which either m–l16 (even l=4,...,10) or m–l=4 (odd l=5,...,15).  相似文献   

12.
We present the coordinates, apparent magnitudes, and morphological types for 230 galaxies presumably identified with HIPASS (HI Parkes All-Sky Survey) sources. The new optical counterparts of the HIPASS sources follow the well-known statistical relationships between the hydrogen mass, luminosity, and type of galaxies. Low-surface-brightness galaxies constitute a significant fraction among these objects. The median value of the hydrogen mass-to-luminosity ratio for them is a factor of 2 or 3 higher than that for bright HIPASS galaxies, reaching 1.7M ⊙/L ⊙. A number of our objects are located near the boundary log(M HI/L B ) = 0.2(M B + 20) that defines the zone of gravitational stability of disk galaxies against large-scale star formation.  相似文献   

13.
The catalog of equatorial coordinates α and δ and B-magnitudes of stars of the northern sky (from–4° to +90°) was created as a part of the FON project at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. The data accumulated in the Joint Digital Archive of the Ukrainian Virtual Observatory were used. The total number of processed plates is 2260. Astronegatives were digitized with Microtek ScanMaker 9800XL TMA and Epson Expression 10000XL scanners in the 1200 dpi scanning mode. The majority of plates have a size of 30 × 30 cm (13000 × 13000 pixels). The catalog contains the data on 19451751 stars and galaxies with B ≤ 16.5m at the epoch of 1988.1. The coordinates of stars and galaxies were obtained in the Tycho-2 reference system, and B-magnitudes were determined in the system of photoelectric standards. The mean internal errors of the catalog are σαδ = 0.23″ and σB = 0.14m for all objects or σαδ = 0.10″ and σB = 0.07m for stars in the B = 7m–14m range. The convergence between the catalog and Tycho-2 is characterized by the following values: 0.06′′ and 0.15m. The mean-square difference in coordinates from the catalog and from UCAC-4 is σαδ = 0.30′′ (18 742 932 objects, or 96.36% of stars and galaxies, were cross-identified).  相似文献   

14.
Finding charts, coordinates, B magnitudes, and U – B color estimates are given for 110 faint blue galaxies located near the centre of the Virgo cluster of galaxies. The galaxies have been found by blinking on plates taken with the Tautenburg 52 inch SCHMIDT telescope.  相似文献   

15.
We present the results of a photometric study of 85 objects from the updated sample of galaxies residing in the nearby Lynx-Cancer void. We perform our photometry on u, g, r, and i-band images of the Sloan Digital Sky Survey. We determine model-independent galaxy parameters such as the integrated magnitudes and colors, effective radii and the corresponding surface brightness values, optical radii and Holmberg radii. We analyze the radial surface brightness profiles to determine the central brightness values and scale lengths of the model disks. We analyze the colors of the outer parts of the galaxies and compare them with model evolutionary tracks computed using the PEGASE 2 software package. This allowed us to estimate the time T SF elapsed since the onset of star formation, which turned out to be on the order of the cosmological time T 0 for the overwhelming majority of the galaxies studied. However, for 13 galaxies of the sample the time T SF does not exceed T 0/2 ～ 7 Gyr, and for 7 of them T SF ? 3.5 Gyr. The latter are mostly unevolved objects dominated by low-luminosity galaxies with M B > ?13.2. We use the integrated magnitudes and colors to estimate the stellar masses of the galaxies.We estimate the parameter M(H I)/L B and the gas mass fractions for void galaxies with known HI-line fluxes. A small subgroup (about 10%) of the gas-richest void galaxies with M(H I)/L B ? 2.5 has gas mass fractions that reach 94–99%. The outer regions of many of these galaxies show atypically blue colors. To test various statistical differences between void galaxies and galaxies from the samples selected using more general criteria, we compare some of the parameters of void galaxies with similar data for the sample of 195 galaxies from the Equatorial Survey (ES) based on a part of the HIPASS blind HI survey. The compared samples have similar properties in the common luminosity interval ?18.5<M g < ?13.5. The faintest void galaxies differ appreciably from the ES survey galaxies. However, the ES survey also contains about 7% of the so-called “inchoate” galaxies with highM(H I)/L B ratios, most of which are located far from massive neighbors and are probably analogs of void galaxies.  相似文献   

16.
Hα luminosities of a sample of galaxies in nearby compactgroups are presented. Our purpose is to study the influence of thegroup environment on the star formation rates (SFRs) of the galaxies in thegroups, provided that the Hα luminosity is a good tracer of theSFR of disc galaxies. Measuring the global L /L B of the groups – including early-type galaxies – we find that the average value of the Hα emission is not significantly different from thatmeasured for field galaxies, and that most of the groups that show thehighest level of L /L B, with respect to a set of synthetic groups built out of field galaxies, show tidal features in at least one of their members. Finally, we have exploredthe relationship between the ratio L /L B and severalrelevant dynamical parameters of the groups (velocity dispersion, crossingtime, radius and mass-to-luminosity ratio) and have found no clearcorrelation. This suggests that the exact dynamical state of a groupdoes not appear to control the SFR of the group as a whole. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

17.
We consider the various methods used to constrain the possible field strength of the present day intergalactic field and findB 0(G)<10–10 as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies.  相似文献   

18.
In order to see whether the study of redshift distribution in different classes of extragalactic objects, suspected of belonging to different phases in the evolutionary sequence of galaxies, helps in arriving at a possible picture of the evolutionary sequence of galaxies, histograms have been plotted between the number and the redshift for each of the five classes of extragalactic objects, namely, the QSOs, N-galaxies, Seyfert galaxies, radio galaxies and normal galaxies. It is found that: (i) the highest peaks in the five histograms occur at distinctly different redshifts in the order (Z peak)QSOs>(Z peak)N-galaxies>(Z peak)Seyfert galaxies>(Z peak)radio galaxies> (Z peak)normal galaxies and (ii) sufficient overlap occurs in the redshift ranges of (a) QSOs and N-galaxies, (b) N-galaxies and Seyfert galaxies, (c) Seyfert galaxies and radio galaxies and (d) radio galaxies and normal galaxies. These facts suggest that the extragalactic objects might be evolving in the sequence: QSOsN-galaxiesSeyfert galaxiesradio galaxiesnormal galaxies. Other independent evidences in support of such an evolutionary sequence have been given. Finally, various aspects of the problem associated with the picture of the evolutionary sequence of galaxies have been critically examined.  相似文献   

19.
This paper presents a statistical investigation of 999 blue objects [U(–B) 0.00, limiting magnitude U = 20, B = 21], the majority of which is newly discovered on M31-plates (predominantly taken by F. Börngen ) of the large Schmidt telescope of the Karl Schwarzschild Observatory Tautenburg. A list of the objects is given elsewhere [G. A. RICHTER (1973)].For “very blue objects” [(U – B) -0.40] the number per square degree brighter than magnitude B is as follows: log NB = 0.72 B -13.1 (starlike objects), log NB = 0.63 B -12.0 (diffuse and probably diffuse objects). This confirms the results of other authors: log NB increases more rapidly than in the case of constant density (0.6); there are about 10 QSOs brighter than B = 20 per square degree. A detailed discussion concerning the optical identification of discrete radio sources will soon be given.  相似文献   

20.
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   

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