Byurakan Survey Research Articles

The cold gas properties of Markarian galaxies

A sample of 61 Markarian galaxies detected in the CO line was compiled. Using available HI, H2, optical and radio continuum data, the analysis of the gas kinematics and the star formation properties for this sample of galaxies was performed. The main conclusion can be summarized as follows: (1) The HI and CO line widths are well correlated. Interaction between galaxies has no influence on the CO line broadening. A rapidly rotating nuclear disk in the galaxy might lead to the CO line broadening with less influence on the HI line. (2) The atomic and molecular gas surface densities are well correlated with the blue, FIR and radio continuum surface bright- ness; however, the correlation for molecular component is stronger. (3) In general, the galaxies with UV-excess (Markarian galaxies) do not dier in their star formation properties from the non-UV galaxies.

Spectroscopic Study of Multiple IRAS Galaxies

Spectroscopic observations by the 2.6 m BAO telescope of IRAS galaxies identified on the basis of the First Byurakan Survey (BIG objects) are reported. Slit spectra were obtained for 16 objects, including components of 7 multiple systems and 2 individual galaxies. The red shifts were measured, and the radial velocities, distances, absolute stellar magnitudes, and infrared and far infrared luminosities were calculated. A diagnostic diagram has been constructed based on the intensity ratios of emission lines and the activity types of the objects have been determined. Two LINERs, five galaxies with composite spectra (Comp, one of which has Sy2 features) and seven HII regions were found. Two objects are ultraluminous IR galaxies (ULIG). It is shown that all the multiple systems are physical pairs or groups. The observed high IR luminosity confirms the view that ULIG/HLIGs may be associated with interactions of galaxies.

The Most Oxygen-Poor Planetary Nebula

PNG135.9+55.9 is a halo planetary nebula recently discovered among the objects from the Second Byurakan Survey. Based upon our first observations, a photoionization model analysis shows that the oxygen abundance in the nebula must be extremely low, probably 10-2–10-3 of the solar value. This finding has strong implications on our understanding of the formation of planetary nebulae, of mixing processes in the stellar progenitors and of the evolution of the Galactic halo.

Spectroscopic Study of a Large Sample of Galaxies Discovered in the Second Byurakan Survey Fields

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]λ3727/Hβ and [OIII]λ5007/Hβ emission-lines ratios, the equivalent widths of [OII]λ3727, [OIII]λ5007 and Hβ emission-lines, and the C[OII]-CHβ 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.

Studies of Second Byurakan Survey Galaxies. II. Comparison of Ultraviolet-excess and Emission-line Techniques

The Second Byurakan Survey (SBS) has been defined using two indicators of activity as observed on objective-prism spectra: the presence of UV excess (UVX) in the continuum, or the presence of emission lines (ELs). Of the ~3500 objects in the survey, 1401 are classified as galaxies. This paper reports on a comparative study of 524 UVX SBS galaxies and 340 EL SBS galaxies. The parameters used for the comparison were apparent magnitude, redshift, spectral class, luminosity, morphology, activity type, and close environment. The main results are as follows:

Confirmation of SBS 1150+599A as an Extremely Metal-poor Planetary Nebula

SBS 1150+599A is a blue stellar object at high Galactic latitude discovered in the Second Byurakan Survey. New high-resolution images of SBS 1150+599A are presented, demonstrating that it is very likely to be an old planetary nebula in the galactic halo, as suggested recently by Tovmassian et al. An Hα image taken with the WIYN 3.5 m telescope and its tip-tilt module reveals the diameter of the nebula to be 92, comparable to that estimated from spectra by Tovmassian et al. Lower limits to the central star temperature were derived using the Zanstra hydrogen and helium methods to determine that the star's effective temperature must be higher that 68,000 K and that the nebula is optically thin. New spectra from the Multiple Mirror Telescope and Fred L. Whipple Observatory telescope are presented, revealing the presence of strong [Ne V] λ3425 lines, indicating that the central star temperature must be higher than 100,000 K. With the revised diameter, new central star temperature, and an improved central star luminosity, we can constrain photoionization models for the nebula significantly better than before. Because the emission-line data set is sparse, the models are still not conclusive. Nevertheless, we confirm that this nebula is an extremely metal-poor planetary nebula, having a value for O/H that is less than 1/100 solar, possibly as low as 1/500 solar.

Studies of the Second Byurakan Survey Galaxies. I. Mergers, Interacting Systems, and Close Pairs

This paper reports on a study of the morphological characteristics of several samples of galaxies drawn from the 1401 objects which comprise the Second Byurakan Survey (SBS). These samples have been chosen to provide information for studies of the relation between galaxy interactions and galaxy star formation activity. Our samples include 110 SBS galaxies in 107 mergers, 58 SBS galaxies in 47 interacting systems, and 49 SBS galaxies in 30 close pairs (projected separations ΔD ≤ 50 kpc and radial velocity differences ΔV ≤ 600 km s -1). Data are also presented for eight SBS galaxies forming four wider pairs (ΔD ≤ 100 kpc and ΔV ≤ 700 km s -1), and 15 SBS galaxies forming five triplets (ΔD ≤ 100 kpc and ΔV ≤ 900 km s -1). Four, and possibly another three SBS galaxies, may be satellites of larger galaxies. Finally, six other SBS objects are possibly H II regions in their host galaxies.

Digitization of the FBS: Its Future Use and Expected Results

Abstract The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. Its plates contain low-dispersion spectra for some 20,000,000 objects. The FBS spectra allow selection of objects by their color, broad emission or absorption lines, or SED; to discover, classify and investigate them. The FBS was conducted originally to search for UVX galaxies (1500 Markarian galaxies were discovered). Selection of blue stellar objects, red stars, and identification of IRAS sources have also been done by means of the FBS spectra. All these projects have been carried out by visual inspection of the plates. Digitization will give new possibilities to search for many new objects: new bright QSOs (m<18m), new Markarian (UVX) galaxies, BCDGs, optical counterparts of IR, radio, X-ray and other sources, late-type stars, planetary nebulae, emission-line stars, and white dwarfs; and to study star clusters and clusters of galaxies. The digitized FBS will be available via the Internet and on CDs. Software and an appropriate interface for working with the data will be provided.

The FIRST-APM QSO Survey (FAQS) in the SBS Region. Current Status

AbstractAs the first step of the Multiwavelength AGN Survey (MWAS), we have started the FIRST-APM QSO Survey (FAQS). The main goal of FAQS is to compile the most complete sample of bright QSOs, located in the area of the sky covered by the Second Byurakan Survey (SBS). Here we report the current status of an ongoing study based on the cross-identification of the FIRST radio catalog and the APM optical catalog. The overlapping sky area between FIRST and SBS is about 700 deg2. The compiled list of sources for this overlapping region contains ~ 400 quasar candidates brighter than . About 90 objects were already spectroscopically classified. During 1999-2000, we observed spectroscopically more than 150 FAQS objects with the 2.1m telescope of the Guillermo Haro Astropysical Observatory (GHAO). We have found 51 new QSOs (4 BAL QSOs), 13 Seyfert Galaxies (5 NLSyl’s), 23 emission line galaxies, 3 BL Lac objects and 57 stars.

Comparison of ELG and UV Galaxies from the SBS Survey

AbstractIn this paper we compare the results of spectrophotometric observations for more then 40 emission line galaxies (ELG) without UV-excess and 70 galaxies with UV-excess (UV-galaxies) from the Second Byurakan Survey (SBS) carried out with the scanner on the 6-m telescope of the Special Astrophysical Observatory. The comparison was aimed to answer the questions: are there any essential differences between these two types of galaxies? And what is the fraction of AGN among ELG and UV-galaxies? To answer this question we have investigated some physical parameters. Great care was taken in classifying the spectra of these galaxies as “HII region-like or “AGN-like” using a new diagnostic method for emission-line galaxies (Rola et al.). We find that 14% of emission line galaxies (ELG) have Sy2 and LINER-like spectra. The transition or ambiguous objects among them comprise 20%. The fraction of LINER-like and Sy2 objects among UV-galaxies is 21% while that of the transition or ambiguous objects in UV-galaxies is 28%. From SBS galaxies, 18% are Sy2s and LINER-like galaxies.

Objective-Prism Emission-Line Searches for Active Galactic Nuclei

AbstractObjective-prism surveys for UV-excess and emission-line objects, especially the First and Second Byurakan Surveys, have been central to the study of active galactic nuclei (AGNs). We review previous line-selected surveys for AGNs and discuss their contribution to our understanding of the AGN phenomena. In addition, we present results from the KPNO International Spectroscopic Survey, a modern digital objective-prism survey for emission line objects. This survey is discovering substantial numbers of new AGNs, in particular low-luminosity AGNs and LINERs.

The Second Byurakan Survey - The Final Results. The Multiwavelength AGN Survey in the SBS Area

AbstractOn the basis of the Second Byurakan Survey (SBS) we have produced the largest and most homogeneous new complete samples of faint Markarian galaxies, Sy galaxies and bright QSOs. The General Catalogue of the SBS Survey, which is completed and prepared for publication, contains the data for more than 3600 objects, half of which are star-like objects while the other half are galaxies. Nearly 2500 slit spectra were obtained for about 2100 SBS objects. 561 new QSOs and AGNs in the magnitude range 15.5 < B < 19.5 with redshifts 0.0 < z <3.2 were spectroscopically confirmed. A sample of 17 BLL has been isolated as well.The volume for reliable investigation of faint Markarian UVX galaxies has been extended out to a distance of about ~ 500 Mpc, more than 50 times deeper than in the FBS. Faint Markarian UVX galaxies from the SBS survey comprise ~ 12% of field galaxies, slightly greater than in the First Markarian survey; ~ 10% of them (~ 120) turned out to be Sy galaxies.A complete sample of faint (B ≤ 17.0, z ≤ 0.1) Sy galaxies has been constructed. In the spatial volume with radius of about 500 Mpc, the relative number of AGNs is 1.2% of field galaxies. One of the most complete and representative samples of bright QSOs (~ 130) in the magnitude range 15.7 < B ≤ 17.5 with redshifts 0.3 ≤ z ≤ 2.2 has been constructed as well.The objects in the combined complete sample of SBS Sy galaxies and QSOs might be roughly divided into two groups: classical Sy galaxies and QSOs in agreement with the previous classification scheme and nonclassical SyG and QSOs for which the existing classification scheme is not sufficient for their classification. The presence of narrow line QSOs (NLQSOs) or so-called QSO II type objects is established. There is a continuous transition of all properties between all types of Sy galaxies and QSOs, from Liners through Sy2, NLSyls, BLSyl to NLQSOs and BLQSOs.Preliminary results from the Multiwavelength AGN Survey (MWAGN) in X-ray, Radio and IR wavebands in the SBS area are presented. The MWAGN survey in the SBS area shows that the ROSAT or FIRST surveys by themselves cannot represent the whole AGN/QSO sample. The ROSAT Bright sources along with the FIRST sources comprise only 25% of the whole SBS QSO sample. The IRAS survey is effective for a redshift less than z < 0.05. All classical Sy2s but only ~ 50% of classical Syls are IRAS sources. Luminous and Ultraluminous IRAS SBS AGNs comprise ~ 25% of the whole AGN sample. The greater part of SBS AGN/QSOs are neither ROSAT nor FIRST nor IRAS LIG or ULIG sources. They are optically emitting AGN/QSOs.The multiwavelength “complete” sample of bright QSOs in the SBS area allows us to conclude that the fast evolution of bright QSOs is more likely the result of a selection effect than the result of fast cosmological evolution. The LogN-B relation for these QSOs reduces to the value LogN − B = 0.67 ± 0.005.A direct empirical estimate of the effect of overlapping images is obtained from the MWAGN survey. The effect of overlap comprises ~ 5% for QSOs brighter than B ≤ 17.0 and ~ 10% for QSOs brighter than B ≤ 17.5.

Spectroscopy and Photometry of Stellar Objects from the Second Byurakan Survey

The results of spectroscopic observations of 202 stellar objects, and photometric observations of 171, from the Second Byurakan Survey (SBS) are reported. The SBS sample has proved to be a rich source of newly identified quasars, Seyfert-type galaxies, degenerate stars, and hot subdwarfs. In this subsample we have identified 71 new QSOs; one BL Lacertae object; one Seyfert 1 galaxy; one LINER; one blue compact galaxy; 31 white dwarfs (WDs), 25 of DA type and six of DB type; 26 subdwarfs; 11 horizontal-branch B-type, 11 normal/horizontal-branch, 18 G-type, and 11 F-type stars; 10 objects with composite spectra; two cataclysmic variables; and six objects with continuous spectra. Among the 71 QSOs, we have found three broad absorption line QSOs, namely, SBS 1139+534, 1524+517, and 1524+491, and one damped Lyα QSO, SBS 1425+606. The very luminous objects have visual magnitudes in the range 15.9 MV > -31.5. A number of the low-redshift SBS QSOs show strong Fe II complexes at rest wavelengths of 4570, 5190, and 5320 A. We present accurate positions, spectral classifications, and magnitudes for all objects. The redshifts, equivalent widths, and spectra for QSOs and emission-line galaxies are given, as are some typical spectra for hot stars. The vast majority (63%) of stellar objects selected in the SBS turned out to be WDs (36%) and sdB subdwarfs (27%). Only ~5%–7% of objects with B < 16.4 and ~13% with B ~ 17.0 were identified as QSOs. In total, 470 QSOs and ~500 hot stars were discovered in the course of the SBS. The lower limit on the surface density of bright QSOs in the redshift range 0.3 < z < 2.2 is no fewer than 0.06 deg-2 for B < 17.0 and 0.13 deg-2 for B < 17.5. The surface density of DA WDs is estimated to be 0.06 deg-2 for B < 16.0 and 0.14 deg-2 for B < 17.0.

Environment status of blue compact galaxies and trigger of star formation

The work studies ?? of the environment of low-mass galaxies with active star formation (SF) and a possible trigger of SF bursts due to gravitational interaction. Following the study by Taylor et al. (1995), we extend the search for possible disturbing galaxies of various masses to a much larger sample of 86 BCGs from the sky region of the Second Byurakan survey (SBS). The BCG magnitudes and radial velocities are revised and up-dated. The sample under study is separated by the criteria: EW((Oiii)5007) > 45 Aa ndVh < 6 000 km s 1 and should be representative of all low-mass galaxies which experience SF bursts. We argue that the moderate tidal disturbers should be taken into account, and incorporate the respective range of distances in the search for disturbing neighbours. The majority of the neighbours in the vicinity of the studied BCGs are found through the study of their environment among UZC (Falco et al. 1999) galaxies, and the follow-up careful search of the fainter galaxies in the NED database. For the remaining BCGs, the neighbouring galaxies are found based on the results of the SAO 6 m telescope spectroscopy. By studing the data on the radial velocities of galaxies in the vicinity of BCGs we found: 1) 33 of the studied BCGs (38:5%) are associated with signicantly brighter galaxies (B 1.5 m ); 2) 23 BCGs (26:5%) have neighbours either of comparable or signicantly lower brightness; 3) 14 of the studied BCGs (16%) with no evident associated galaxy are either certain, or probable, mergers. Summarizing, we conclude that in80% (or more) BCGs from the studied sample, the SF bursts are triggered either by tidal action of various strengths from other galaxies, or due to mergers of low-mass galaxies. We briefly discuss the implications of our main conclusion for evolutionary links of BCGs to other types of low-mass galaxies. Part of our sample falls into the belonging to the Local Supercluster. Therefore we formulate the results separately on the \Local Supercluster volume and \general eld region. The total fractions of BCGs likely triggered by interaction with other galaxy are respectively,84:5% and 80% for the nearby and for the general eld. The fractions of BCGs with signicantly brighter disturbers in these two groups are seemingly dierent (5414% vs.31:57%, respectively). Among the so called \isolated BCGs (that is, without a bright neighbouring galaxy) in both the Local Supercluster and in general eld,4310% are probably disturbed by dwarf galaxies and268% have a merger morphology. In the Appendix we present the results of the spectroscopy with the SAO 6 m telescope of 27 galaxies in an attempt to nd possible disturbing galaxies in the vicinity of some of the sample BCGs.

Hα emission line morphologies in Markarian starburst galaxies

We present broad band R and narrow band H alpha emission line images of a sample of optically selected starburst galaxies from the Markarian lists. The emission line morphology is studied and global properties like luminosities, equivalent widths and star formation rates are derived. The radial distribution of Hot flux and the EW are determined using concentric aperture photometry on the emission line and the continuum images. Ha flux is generally found to peak in the nuclear region and fall off outwards. The EW is found to peak off-center in most of the cases implying that though the intensity of emission is maximum at the nucleus, the star formation activity relative to the underlying continuum often peaks away from the center in Markarian starburst galaxies.

SBS 1150+599A: An extremely oxygen-poor planetary nebula in the Galactic halo?

We report results of a spectrophotometric study of SBS 1150+599A and discuss the nature of this object based upon our data. Our study shows that SBS 1150+599A is most probably a planetary nebula located in the Galactic halo and not a cataclysmic variable as originally proposed by the authors of the Second Byurakan Survey from low resolution spectroscopy. We have further elaborated on the properties of SBS 1150+599A (now becoming PN G135.9+55.9) with tools used for planetary nebula analysis. Our photoionization models show that, in order to match the observational constraints, the oxygen abundance in the nebula is probably extremely low, around 1/500 solar, which is one order of magnitude lower than the most oxygen-poor planetary nebulae known so far. This finding has strong implications on our understanding of the formation of planetary nebulae and of the evolution of the Galactic halo.

Structural Parameters and Morphology of a Subsample of BCGs from the First and Second Byurakan Surveys

We present CCD B,V and R surface photometry for a subsample of 67 blue compact galaxies (BCGs) drawn from the First and Second Byurakan surveys. We outline the range of typical photometric parameters for the investigated subsample. The surface brightness profiles were built for all BCGs. The profile decomposition was done using two-component model: an exponential disk and/or a gaussian component at small effective radii. The (B-V) and for the part of galaxies (V-R) color profiles were derived. The analysis shows the variety of morphologies, and large range of galaxy sizes and exponential disk structural parameters. We use these data to check possible correlations between various physical parameters and gain insight into star-forming processes in BCGs. We compare structural parameters for our BCGs to those of other types of dwarf galaxies – dIrr, dE and LSBD galaxies to look for possible connections between them and BCGs.

Investigation of Galaxies of the Second Byurakan Sky Survey. IV. Spectroscopic Observations in the Fields of 11h30m, +59° and 12h00m, +59°

Spectroscopic observations of 71 objects have completed the follow-up spectroscopy of galaxies in two adjacent fields of the Second Byurakan Survey with central coordinates α = 11h30m, δ = +59° and α = 12h00m, δ = +59°. The spectra were obtained on the 2.6-m telescope of the Byurakan Astrophysical Observatory and the 6-m telescope of the Special Astrophysical Observatory. The redshifts and absolute stellar magnitudes of all the galaxies have been determined. The objects have been classified using an adapted scheme.

Surface Density of Bright, Active Extragalactic Objects

A new sample of local, active extragalactic objects has been compiled: a combined sample that is the sum of two samples, of Sy1 galaxies and of quasars from Markarian's survey and quasars from the Bright Quasar Survey. A log N(<B)-B relation is constructed for the new sample of active galaxies, limited to the apparent stellar magnitude B = 15 m .5. It can be represented by a straight line with a slope β = 0.60 ± 0.06. It is a good extension, without a noticeable jog, of the analogous relationship for the Hamburg—ESO survey, which has a slope β = 0.59 ± 0.04. The combined surface density of bright active galaxies and quasars down to B = 15 m .5 is 0.01 per square degree.

The Morphologies of Dwarf Markarian Galaxies

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.