A Catalog of Very Isolated Galaxies from the SDSS Data Release 1

We present a new catalog of isolated galaxies obtained through an automated systematic search. These 2980 isolated galaxies were found in approximately 2099 sq deg of sky in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1) photometry. The selection algorithm, implementing a variation on the criteria developed by Karachentseva in 1973, proved to be very efficient and fast. This catalog will be useful for studies of the general galaxy characteristics. Here we report on our results.Comment: 67 pages, which includes 14 figures. Accepted for publication by A

The Low-Redshift Lyman Alpha Forest toward PKS 0405-123

We present STIS 7km/s resolution data of the Ly-a forest toward PKS0405-123 (z=0.574). We make two samples. The strong sample (60 systems) has column density logNHI>13.3 over 0.002<z<0.423, and the weak sample (44) has logNHI>13.1 at 0.020<z<0.234; 7 absorbers show metals, all with OVI, but often offset in velocity from HI. The strong sample Doppler parameters show =47+-22km/s; for the weak, =44+-21km/s. Line blending and s/n effects likely inflate b. The redshift density dN/dz is consistent with previous, lower resolution results for logNHI>14.0. For 13.1<logNHI<14.0, we find a dN/dz overdensity of ~0.2-0.3 dex at 0.127<z<0.234, which we believe arises from cosmic variance. We find Ly-a clustering over Delta v13.3, consistent with a numerical model. There is a void in the strong sample at 0.0320<z<0.0814. We detect radial velocity correlations for Delta v<250km/s between Ly-a absorbers and 39 galaxies in a 10' field. The correlation grows with minimum NHI, peaking for logNHI ~> 13.5-14.0. The strength is similar to that of the galaxy-galaxy correlation for our sample, implying that such Ly-a systems have mass log M/Msun= 11.3+1.0-0.6. Including lower column density systems in the sample shows correlations only out to Delta v <125km/s, as would be expected for smaller density perturbations. Galaxy counts and local HI column density appear correlated, peaking at ~5000km/s. We also give column densities for Galactic species. (Abridged)Comment: 59 pages, 6 tables, 14 figures, 1 standalone, ApJ, in press; minor revisions/clarifications for acceptance, including galaxy lis

A study of the large voids in the spatial distribution of galaxy clusters in the Northern Galactic Hemisphere


We present a mapping of the large voids ($D \geq$ 50 $h^{-1}$ Mpc) in the spatial distribution of clusters of galaxies in the Northern Galactic Hemisphere in a volume defined by galactic latitude $b \geq$ +30$^{\circ }$ and redshift $z \leq$ 0.14. Rich clusters with spectroscopically measured or photometrically estimated redshifts are used as tracers of the large-scale structure of the Universe. An automated void-search and analysis procedure which identifies a void as a system of intersecting empty spheres is applied, allowing for a description of the void dimensions, volumes and shapes more complete than in previous investigations. A number of void catalogues corresponding to different tracer types, different sources of redshift data, and different versions of the search method have been generated and analysed. Visualizations of the 2-D and 3-D distributions of voids are presented. The estimated mean dimensions of the voids of $R \geq$ 1 and $R \geq$ 0 Abell/ACO clusters are $D_\mathrm{e}$ = 105.0 ± 5.6 $h^{-1}$ Mpc and $D_\mathrm{e}$ = 87.2 ± 4.1 $h^{-1}$ Mpc, respectively, where $D_\mathrm{e}$ is the equivalent void diameter. We have identified the poor clusters, groups, and galaxies populating the voids of rich clusters and constructed radial density profiles of the voids, which show the presence of a void hierarchy.

Photometric study of the FUor star V 1735 Cyg (Elias 1-12)

Results from optical photometric observations of the PMS star V 1735 Cyg are reported. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from IRVB CCD photometric observations of the star collected from Introduction V 1735 Cyg (Elias 1-12) was discovered by IRVB light curves of V 1735 Cyg in the period . The arrows mark the upper limits from photographic observations made with Palomar, Tonantzintla and Rozhen Schmidt telescopes Results and Discussion Using the collected data from photographic and CCD observations we try to construct the historical light curve of V 1735 Cyg and to study the photometric behavior of the star around the optical outburst and in the time of set in brightness. The analysis of the available photometric data for V 1735 Cyg leads to some important conclusions. The time of rise in brightness and the star magnitude in the maximum light are still under discussion. The data from photographic observations made with the 50/70-cm Schmidt telescope from 1986 to 1992 show a strong light variability (∆V = 1 m .2). Taking into account the magnitudes from We find the photometric studies of FUor and FUor-like objects as very important for their exact classification. The problems with duration and possible recurrence of FUor stage can by solved by collecting photometric data from the photographic plate archives and with photometric monitoring in the present time. Another disputed point that can be solved by photometric monitoring of star forming regions is the percentage of PMS stars passing through a FUor outburst. Acknowledgements

A long-term photometric study of V 1184 Tauri

Aims. The main purpose of our investigation is to construct the long-time light curve of the PMS star V 1184 Tau. We consider the study of the photometrical variability of PMS stars as very important for understanding stellar evolution. The unusual photometric variability of V 1184 Tau was reported in previous studies as well, but the nature of the observed deep minima is still under discussion. Methods: We present recent data from CCD photometry and from archival photographic plates. The photometric BVRI data presented in this paper were collected from November 2005 to November 2007. To construct the historical light curve of V 1184 Tau, a search for archived photographic observations in the Wide-Field Plate Database (WFPDB) was made. As a result, 412 photographic plates were found containing the field of V 1184 Tau. A part of the plates were scanned at our request and a magnitude estimation was made of V 1184 Tau. Results: Our recent photometric data suggest that the star brightness is still near the minimum. Thus the period of strong light variations that started in 2003 continues up to the present, hence more than 4 years. Our data from the archival photographic plates suggest that an unknown minimum of brightness exists in the approximate period 1980-1985. Taking all available photometric and spectroscopic data into account we must reject the hypothesis that V 1184 Tau is an FU Orionis type object. V 1184 Tau is a G type low-mass star whose spectrum is similar to WTT stars, but its photometric behavior is typical of the UX Orionis variable stars. Assuming the obscuration from orbiting dust clouds as a reason for a deep minimum, we estimate the approximate period of obscurations and the interval between two deep minima. Our calculations give a 25-28 year period between the two minima and approximately 8-10 year duration of the minima