Next Contents


The analysis of catalogs of galaxies has become more and more important for cosmological studies. In order to extract information from galaxy catalogs that is both reliable and useful, they must be as complete and representative as possible in order to control selection effects. In this data paper we describe the properties of the Markarian galaxies, which were identified because of their UV excess. By using the Markarian galaxies as tracers and statistically comparing their properties to a control sample of "normal field galaxies" (A. Petrosian et al. 2007, in preparation), we can investigate a number of problems: morphological classification, distribution of linear diameters, nuclear activity, etc.

The morphological classification of galaxies has long been regarded as an important step toward understanding galaxy formation and evolution (e.g., van den Bergh 1997). There is considerable evidence that the morphological classification directly reflects the physical properties of galaxies (e.g., Roberts & Hayes 1994). Markarian objects can reveal important clues in these investigations since they span a wide luminosity range between -25 and -13 mag and have a very broad range of morphological structure as well as different stages of activity from QSOs to blue compact dwarfs (BCDs).

The luminosity function (LF) of the galaxies is an important constraint for models of cosmic structure formation and is fundamental to observational cosmology. The dependence of the LF on observable parameters such as morphology, color, etc. provides further information for the models. Wide-angle surveys at relatively bright apparent magnitudes allow the most detailed investigations of individual galaxy properties and remain the best approach for measuring the local LF and its variation from one part of the universe to other (e.g., Ellis 1997; Cross et al. 2001). The Markarian survey is one of the well-known wide-angle surveys, and it has previously been used to study this particular subject (e.g., Huchra 1977). We shall rederive the LF using our updated properties and improved statistics.

The statistical distribution of linear diameters is essential both for an understanding of galaxy structure and formation and also as a tool to probe the cosmological models. Growing interest in the diameter distribution function has been motivated by several problems related to studies of large-scale structure such as the determination of the optical dipole (e.g., Lynden-Bell et al. 1989), estimates of cluster distances from diameter information only (e.g., Lahav & Gull 1989), the reconstruction of the density field from diameter-limited catalogs (Maia & da Costa 1990; Dressler 1991; Bardelli et al. 1991; Hudson & Lynden-Bell 1991), determination of local redshift-distance law (e.g., Segal & Nicoll 1997), and in combination with other parameters as a tool for the independent check on the value of the Hubble constant (e.g., Ekholm et al. 1999; Russell 2002). Reflecting the different nature of the Markarian objects, their linear diameters cover broad range of values starting from a few kpc (BCDs) up to a hundred kpc (giant or merging galaxies). Different classes of Markarian objects with different diameter distributions can be useful to study these problems.

Large amounts of observational data have been accumulated in all spectral ranges supporting unified models of AGNs, particularly of Seyfert galaxies (e.g., Hines & Wills 1993; Goodrich et al. 1994; Evans et al. 1993; Tran 1995; Veilleux et al. 1997). The standard unification scheme postulates that the viewing angle of the circumnuclear torus of dust and gas is the only parameter of importance in determining the appearance of all types of Seyfert galaxies. Some papers, however, present results suggesting that not only the orientation of the circumnuclear torus relative to the line of sight, but also torus orientation relative to the host galaxy and host galaxy inclination may be important in AGN classification (e.g., Maiolino & Rieke 1995; Schmitt & Kinney 1996; Schmitt et al. 1997; Simcoe et al. 1997). The galaxy inclination effect may also be crucial for understanding the role of circumnuclear starbursts in AGN phenomena (e.g., Cid Fernandes & Terlevich 1995; Gonzalez Delgado et al. 2001). Since many Markarian galaxies contain AGNs and many more have starburst nuclei, information about their inclination can be important to study these problems.

Various cosmological scenarios related to the origin and evolution of large-scale cosmic systems (clusters and superclusters) predict different distributions for the angular momentum of galaxies, i.e., of the galaxy orientations, which are represented as different forms for the alignment of the galaxies within the systems. A random distribution of the rotation axes of the galaxies is expected in the framework of the major classical evolutionary scenarios of the systems (e.g., Shandarin 1974). On the other hand, fragmentation scenarios (e.g., Ozernoy 1978; Doroshenko et al. 1978) would suggest coherence in the alignments of galaxy orientations. The study of galaxy orientations therefore has the potential of yielding important information on the formation and evolution of the cosmic structures. Previous results of such studies are controversial. Studies have shown that there are coherent alignments of galaxy orientations in some clusters and superclusters, and no coherent alignment in several others (e.g., Aryal & Saurer 2004). Any alignment of galaxy orientations in these systems may also depend on the structure of the clusters and superclusters (e.g., Kashikawa & Okamura 1992) as well as the morphology of the galaxies (e.g., Wu et al. 1997; Aryal & Saurer 2005). No previous study has investigated whether there is also any correlation of galactic nuclear activity with alignments of galaxy orientations. Since Markarian galaxies are objects with different levels of activity and more than 30% of Markarian objects are members of clusters of galaxies (Petrosian & Turatto 1986a, 1986b), this sample will be valuable for such a study. Galaxies position angle information is crucial for such a study (e.g., Hawley & Peebles 1975; Jaaniste & Saar 1978).

The literature describing the influence of local environments on active and star-forming galaxies in the production of AGNs, starburst, and H II nuclei has become voluminous. Kennicutt (1990), Heckman (1990), and Schweizer (1990) reviewed the status of understanding of the relation between galaxy interaction and activity or enhanced star formation in galaxies. Recent studies add more data on the subject (e.g., Hashimoto et al. 1998; Iglesias-Paramo & Vilchez 1999). Data at different wavelengths provide evidence that close environments and interactions may trigger activity or bursts of star formation in the nuclei of galaxies. Nevertheless, the results of different investigations depend strongly on the adopted tracers of the activity and star formation (optical, IR, radio, etc.) and also very strongly on the samples on which the analyses were performed (e.g., Leech et al. 1994; Vilchez & Iglesias-Paramo 1998; Allam et al. 1999; Krongold et al. 2002). The UV excess radiation of Markarian objects mostly originates from AGNs or enhanced star-forming regions, and many of these objects are in close interaction or in the dense galactic environment. The study of such systems can help address these problems.

In summary, we have an extensive list of scientific problems that can be studied using the various parameters of Markarian galaxies. This paper describes a new database for 1544 Markarian objects containing the following new measurements: accurate optical positions, morphological classes, apparent magnitudes (red and blue), diameters, axial ratios and position angles, and counts of neighbor galaxies within 50 kpc radius based on the galaxy redshift and assuming a value for the Hubble constant of H0 = 75 km s-1 Mpc -1. We also provide extensive notes indicating isolation or the membership of Markarian galaxies in clusters, groups, triplets, or pairs of galaxies. In addition, we have compiled from the literature updated spectral and activity classes as well as new and revised determinations of redshifts that were required for distance estimates for all galaxies. At the request of an anonymous referee, we have also included the corresponding near-IR magnitudes for all the galaxies from the 2MASS or DENIS surveys and Galactic E(B - V) values. This will facilitate comparison of the optical and near-IR properties of galaxy subsets.

In Section 2 of this paper we describe the Markarian survey and some results. It also describes used observational material and the generation of the database. The database itself and related notes are described in Section 3. In Section 4 an atlas of several interesting subclasses of Markarian galaxies is presented. Future papers in this series will describe the statistical analyses that are already underway addressing some of the interesting problems described in this introduction. In particular, two studies addressing the problem of origin and evolution of the clusters of galaxies containing Markarian objects, and the influence of local environment on barred spiral Markarian galaxies, will be presented soon.

Next Contents