Sternberg Astronomical Institute Supernova Catalogue and Radial Distribution of Supernovae in the Host Galaxies O. S. Bartunov, D. Yu. Tsvetkov and N. N. Pavlyuk Sternberg Astronomical Institute, Moscow, Russia Abstract. We present Supernova Catalogue and the results of investigation of Supernova radial distribution in the host galaxies based on the new data. We collected the available data on SNe and verified their coordinates, identifications of host galaxies and information about them, which was compiled from different sources and included in our catalogue. We corrected many errors in previous data, and found new data about galaxies. The catalogue is stored in RDBMS and was specially designed following the recommendations of Virtual Observatory. It is planned to make it available as a resource of Virtual Observatory. One of the primary goals is the scaling of our catalogue to include the large number of SNe expected to be discovered by forthcoming projects. We also raise several questions before SN community: the existing nomenclature scheme soon will become insufficient to handle large numbers of SNe; the current way of assigning SN identifications does not satisfy modern state of affairs: many SNe are discovered by closed projects and become available to the community after long time. We confirm the results of our previous study, which found significant differences in distribu- tions of types Ia, Ib/c and II SNe in the central parts of spiral galaxies: low rate of SNe Ia in the innermost parts and relatively high concentration of SNe Ib/c towards the centers of host galaxies. We discuss possibilities of future SNAP mission to provide data enabling to study evo- lution of SNe radial distributions with age and distance and possible improvement of estimates of cosmological parameters using more homogeneous samples of SNe Ia selected on the basis of their position in the host galaxies. 1. Introduction The collection and systematization of SN data and their presentation in a form con- venient for statistical and other studies are of particular interest at present time. The number of SN discoveries increased dramatically in recent years. SNe are widely used as "standard candles" for constructing distance scales and for cosmological studies, some of them may be related to mysterious gamma-ray bursts. The first lists of SNe appeared in late 1950s and were repeatedly updated as the number of discoveries increased (Zwicky 1958, 1965; Kowal and Sargent 1971; Sargent et al. 1974). They presented also the basic data on the host galaxies, and catalogs by Karpowicz and Rudnicki (1968) and Flin et al. (1979) also contained a complete bibliography for each object. In the last twenty years, the Asiago Observatory Catalogue of SNe (Barbon et al. 1984, 1989, 1999) has received the greatest recognition. At present, continuously updated lists and catalogs of SNe can be found on the Internet. Among them we would like to mention the list of SNe maintained by the Central Bureau for Astronomical Telegrams (http://cfa-www.harvard.edu/cfa/ps/lists/Supernovae.html) and the online version of the Asiago Catalogue (http://web.pd.astro.it/supern). Studies of the SN distribution in galaxies are of great interest in elucidating the nature 1 of the stellar populations that provide SN explosions of a certain type. Although the presupernova stars have been detected for several type II SNe, the origin of precursors of other types is still an open question in many respects. Of particular interest is the possible difference between the populations of type-Ia presupernovae in galaxies of different types, ages and chemical compositions, which can affect the results of cosmological studies. Despite the rapid increase in the amount of data, the SN distributions in galaxies have been studied rarely in recent years. After the paper by Bartunov et al. (1992), which provides references to earlier works, we would like to note the papers by van den Bergh (1997), Wang et al. (1997), Howell et al. (2000), Tsvetkov et al. (2004). The latest studies have revealed some unexpected facts: deficiency of SNe Ia in the central parts of spiral galaxies and strong concentration of SNe Ib/c toward the centers, which deserve verification using larger amount of data and interpretation. 2. Supernova Catalogue The SAI Catalogue of SNe was originally intended for statistical studies, its compilation was started in 1986 on the basis of existing SNe lists and published data, it was described by Tsvetkov and Bartunov (1993) and Tsvetkov et al. (2004). Until recently Supernova Catalogue was stored as filebased system. The data on SNe were connected with the data on their host galaxies in the main file of the catalogue: each string presented data on SN and on its host galaxy. At the beginning of 2006 we started transformation of the catalogue to the database structure. We want to abandon traditional table, to follow relational approach and nor- malize data. The main reasons are: There are galaxies with multiple SNe outbursts. In the table the data on these host galaxies• is presented in several lines, corresponding to each SN. So when the information on one galaxy is updated, it is necessary to replace it in several lines. After the division of tasks of updating the data on SNe and on host galaxies this can• be done by different authors. It is possible to insert data on newly discovered SNe quickly and to update information on the galaxies more seldom, when new data become available. Only one author can make changes in the file at certain moment. But with growing num• ber of SN discoveries it is necessary to provide several authors with the possibility to edit the data simultaneously. This becomes possible with the new structure, the jobs of several authors can be duly distributed and coordinated. In the file the data is strictly formatted, and if the information for some SN does not• fit in the format, the structure of all file should be changed. In the database it is possible to foresee future changes, as the data of variable length are permissible. The task of adding new data to the catalogue can be further systematized and divided• into simple parts. Besides dividing all the data into two main tables with infor- mation on SNe: "sn" and on the galaxies: "galaxies", the constant parts of inserted data are presented in separate tables - so called reference tables. While compiling the catalogue we payed special attention to the identification of the host galaxies, which is becoming increasingly difficult because of growing number of faint and distant SNe discovered in recent years. In addition, difficulties arise when a SN explodes in a multiple system or in a peculiar galaxy. Therefore we studied the sky field around each SN using various digital sky surveys. To find the most likely host galaxy, we use data on the radial velocity and brightness of the galaxies and SNe in addition to their sky position. If the host galaxy is multiple, it is specified in the description of the galaxy type, and SNe in such galaxies are excluded from sample for studying the radial distribution. The catalogue will be available for downloading as a text file (compatible with previous versions) and as dump database for installation on any user's computer. In future we plan to make it a resource of Virtual Observatory. 3. Problem of SN designations Working on the catalogue, we have to deal with the currently accepted system of designations. Now it becomes clear that this system cannot meet growing demands. First of all, only 702 SNe per year can be designated, and very soon this number will be exceeded. The sequence of names in many cases does not reflect neither time order of discoveries nor order of outbursts. Besides, some recent projects do not report their discoveries to IAU Central Bureau for Astronomical Telegrams, and these SNe does not receive usual designations. So we suggest that this system should be modified to have enough capacity to designate thousands of SNe per year, it should be compatible with the present system and should provide possibility for closed projects to include their discoveries at any time without disordering the system. To increase the capacity without changing existing scheme we propose to prolong the designations, so after SN2008zz we should have SN2008aaa, SN2008aab, etc. The basic principle is that the year in the designation is the year when discovery image was obtained, not the year of actual discovery. For example, while investigating the SAI plate collection in 2005, Antipin (2005) discovered new SN on plate obtained in 1985. As now the last SN for this year is SN 1985U, this new object should be given name SN 1985V. It is clear, that the time order of discoveries cannot be reflected by the order of SNe names, so if some project makes the list of discovered SNe available after some period past actual observations were made, these SNe should be appended at the end of the list for the year of first SN observations. The SN names given by the project, such as SNLS-04D1ag for SN discovered by SNLS (http://www.cfht.hawaii.edu/SNLS), can be regarded as its proper name and also used for references; our catalogue already includes the table with unique identifications of SNe and their proper names. We also appeal to the teams carrying out specialized SN searches, aimed to investigate, for instance, only SNe Ia, to publish all their discoveries. This is vital for completeness of SN catalogues, for studies of radial distribution of SN and rates of their outbursts. 4. Radial distribution of SNe The method of analyzing the radial distribution is virtually identical to the method that we used previously (Bartunov et al.