I. Introduction

4. Distribution Mode for 2MASS Products

a. On-Line Access

i. The NASA/IPAC Infrared Science Archive (IRSA)

ii. NASA/IPAC Extragalactic Database (NED)

The names, positions and basic photometric information from the XSC have been integrated into the services of the NASA/IPAC Extragalactic Database. NED provides full cross-identification of XSC sources with other extragalactic holdings, and the 2MASS photometry is included in the NED Spectral Energy Distribution databases. 2MASS Extended Source images, including links to the IRSA 2MASS Quicklook Image Server Image Retrieval Service and jpeg previews, are also available in NED. For example, compare the 2MASS images with optical, radio and X-ray images of the NGC 253 galaxy.

b. Electronic Access to Full Catalogs

The 2MASS All-Sky Release Catalogs and Scan Information Table are available in compressed (gzipped) ascii form for bulk download from the NASA/IPAC Infrared Science Archive, at the following site:


Be aware that the catalog tables are extremely large. You will need approximately 43 GB of disk space to download all of the gzipped tables. Because the data volume is so large, it is not practical to access the data with screen editors. For this reason the tables have been formatted in a manner consistent with convenient loading into a database server. The formats of the Catalog and Tables, contents of the ftp site and useful database loading instructions and validation tests are described in the README_ftp.html and contents.html files available on the download site.

The PSC is divided into 92 separate files, each containing source records that fall in 0.1° declination bins starting with -90° declination. Within each declination bin source entries are ordered by increasing right ascension. The XSC is divided into two files, one containing sources with declination < 0° and the other containing sources with declination > 0°. Within each XSC file the source records are ordered by increasing declination. The Scan Information Table is contained in a single file ordered by increasing scan_key.

c. DVD-ROM Catalog Versions

The 2MASS All-Sky Catalogs and Scan Information Table is available on a limited edition DVD-ROM set. These disks contain only the Catalog Tables and are intended for use by professional astronomers and institutions. The DVD set does not contain the Image Atlas. If you are interested in ordering this product, please send us an email with your name, institution, and full mailing address.

[Last Update: 2015 May 5; R. Cutri, further revisions by S. Van Dyk.]

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