This is a catalog of galaxies observed in the X-ray band with the Einstein Observatory imaging instruments, the Imaging Proportional Counter (IPC) and the High Resolution Imager (HRI). The catalog comprises 716 observations of 493 galaxies, including those that were targets of pointed observations, and galaxies from the Revised Shapley-Ames (RSA) Catalog of Bright Galaxies and the Second Revised Catalog (RC2) Catalog of Bright Galaxies that were serendipitously included in Einstein fields, plus X-ray data on 4 other galaxies (LMC, SMC, M 31 = NGC 224, and M 32 = NGC 221) taken from the literature, for a total of 720 entries. A total of 450 of these galaxies were imaged well within the instrumental fields, resulting in 238 detections and 212 3-sigma upper limits. The other galaxies were either at the edge of the visible field of view or were confused with other X-ray sources. This database was created by the HEASARC in January 2002 based on CDS Catalog J/ApJS/80/531, tables gxatlas.dat and gxfluxes.dat. This is a service provided by NASA HEASARC .

This is a new catalog of open clusters in the Galaxy which updates the previous catalogs of Lynga (1987, CDS Cat. VII/92, the HEASARC Browse table now called LYNGACLUST) and of Mermilliod (1995, in Information and On-Line Data in Astronomy, ed. D. Egret & M. A. Albrecht (Dordrecht: Kluwer), 127) (included in the WEBDA database, http://www.univie.ac.at/webda/). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogs, have been included. Virtually all of the clusters presently known are included, which represents a large increase in the number of objects (almost 1,000) relative to the Lynga Catalog. In total, 99.7% of the objects have estimates of their apparent diameters, and 74.5% have distance, E(B-V) and age determinations. Concerning the data on kinematics, 54.7% have their mean proper motions listed, 25% their mean radial velocities, and 24.2% have both information simultaneously. Acknowledgments: Extensive use has been made by the authors of the SIMBAD and WEBDA databases. This project is supported by FAPESP (grant number 03/12813-4) and CAPES (CAPES-GRICES grant number 040/2008). This database table was originally created by the HEASARC in September 2002 based on the CDS version of the catalog. In March 2006, the HEASARC updated the table to use instead the following file obtained from the authors' web site: http://www.astro.iag.usp.br/ocdb/file/clusters.txt. In August 2017, the HEASARC reverted to using the CDS version of this catalog, available as the file clusters.dat at http://cdsarc.u-strasbg.fr/ftp/cats/B/ocl/. This is a service provided by NASA HEASARC .

This catalog is an updated version of the original version of the Lynds' Catalog of Dark Nebulae that was published in 1962. The catalog was based on a study of the red and blue prints of the National Geographic - Palomar Observatory Sky Atlas. The catalog contains positions for the centers of dark nebulae or clouds found by Lynds, values for the cloud sizes in square degrees, visual estimates of their opacity, and cross-identifications to Barnard Objects which are associated with the tabulated clouds. This HEASARC version of the LDN Catalog was created in June 1997. It was derived from CDS Catalog VII/7A obtained from https://cdsarc.cds.unistra.fr/ftp/cats/VII/7A/. Please refer to the CDS "Historical Notes" for details regarding the lineage of this version. Additional information provided in the HEASARC documentation was taken from the original published version of this catalog. This is a service provided by NASA HEASARC .

This study presents a catalog of 8107 molecular clouds that covers the entire Galactic plane and includes 98% of the ¹²CO emission observed within b +/- 5 deg. The catalog was produced using a hierarchical cluster identification method applied to the result of a Gaussian decomposition of the Dame+ (2001ApJ...547..792D) data. The total H₂ mass in the catalog is 1.2 x 10⁹ M_sun, in agreement with previous estimates. The authors find that 30% of the sight lines intersect only a single cloud, with another 25% intersecting only two clouds. The most probable cloud size is R~30pc. In contrast with the general idea, the authors find a rather large range of values of surface densities, Sigma = 2 to 300 M_sun/pc², and a systematic decrease with increasing Galactic radius, R_gal. The cloud velocity dispersion and the normalization sigma₀ = sigma_v / R^1/2 both decrease systematically with R_gal. When studied over the whole Galactic disk, there is a large dispersion in the line width-size relation and a significantly better correlation between sigma_v and SigmaR. The normalization of this correlation is constant to better than a factor of two for R_gal < 20kpc. This relation is used to disentangle the ambiguity between near and far kinematic distances. The authors report a strong variation of the turbulent energy injection rate. In the outer Galaxy it may be maintained by accretion through the disk and/or onto the clouds, but neither source can drive the 100 times higher cloud-averaged injection rate in the inner Galaxy. The data set used in this catalog come from that of Dame+ (2001ApJ...547..792D). Those authors combined observations obtained over a period of 20 yr with two telescopes, one in the north (first located in New York City and then moved to Cambridge, Massachusetts) and one in the south (Cerro Tololo, Chile). These 1.2m telescopes have an angular resolution of ~8.5' at 115GHz, the frequency of the ¹²CO 1-0 line. For the current study the authors used the data set covering the whole Galactic plane with +/- 5 deg in Galactic latitude. This table was created by the HEASARC in March 2019 based upon the CDS Catalog J/ApJ/834/57 file table1.dat. This is a service provided by NASA HEASARC .