The primary journal reference for 2MASS and its image and catalog data products is:
The Two Micron All Sky Survey (2MASS)
M.F. Skrutskie, R.M. Cutri, R. Stiening, M.D. Weinberg, S. Schneider,
J.M. Carpenter, C. Beichman, R. Capps, T. Chester, J. Elias, J. Huchra,
J. Liebert, C. Lonsdale, D.G. Monet, S. Price, P. Seitzer, T. Jarrett,
J.D. Kirkpatrick, J. Gizis, E. Howard, T. Evans, J. Fowler, L. Fullmer,
R. Hurt, R. Light, E.L. Kopan, K.A. Marsh, H.L. McCallon, R. Tam,
S. Van Dyk, and S. Wheelock,
2006, AJ, 131, 1163.
(Bibliographic Code: 2006AJ....131.1163S)
Please include the following standard acknowledgment in any published material that makes use of 2MASS data products:
"This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation."
To order a 2MASS All-Sky Data Release DVD-ROM set, please email your
request to the 2MASS Helpdesk,
and include your full name and mailing address.
Please note: The DVD-ROM contains Catalog data only, and no Atlas
Images or movies. It is intended for use by professional astronomers only.
N.B.: The format of the Catalog files is bar-delimited ascii,
suitable for reading into database packages, such as Postgres, Informix
or Oracle. The user should consult the
All-Sky DVD Release
Updates for the most recent information on the DVD-ROMs.
The DVD-ROM is free of charge.
We know of the following drives which will support our past DVD-ROMs:
Electronic access to the All-Sky Release Catalogs via ftp is described in
Section I.4.b of the on-line 2MASS Explanatory Supplement.
Yes, full-resolution JPG renditions of Atlas Images and Atlas Image mosaics
can be found on the 2MASS
Image Galleries.
Images in the 2MASS Image Galleries are in the public domain, so you are
free to use the images that you download from these sites. However, we ask
that you please use the following acknowledgement, where possible, with the
image:
"Atlas Image [or Atlas Image mosaic] obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts
and the Infrared Processing and Analysis Center/California Institute of
Technology, funded by the National Aeronautics and Space Administration and
the National Science Foundation."
Given the sheer volume of Image data (~10 Terabytes), the production of a
DVD-ROM of this sort is prohibitive. The full-fidelity Atlas Images
can be accessed on-line using the
2MASS Image Services of the
Infrared Science Archive (IRSA).
The Explanatory Supplement for the All-Sky Release is currently
intended to be a "living document", i.e., it will be
modified at frequent intervals, such that a hardcopy soon becomes outdated.
For the All-Sky Data Release, we will offer the Explanatory
Supplement as a single document on the DVD-ROM version of the Release.
However, users should continue to refer to the online version for up-to-date
information.
The full-fidelity (non-lossy-compressed) Atlas Images
are available via the on-line
2MASS Image Services of the
Infrared Science Archive (IRSA).
First a caveat: the 2MASS Atlas Images that are currently available
from the IRSA web services (irsa.ipac.caltech.edu) are lossy-compressed
"Quicklook" versions of the images. The compression algorithm sacrifices
information particularly in the low order bits of the images,
so background levels are compromised. For this reason, we do not
recommend attempting to measure brightness upper limits from
the Quicklook images.
An alternative to estimating upper limits for
non-detected sources would be to examine the properties of the 2MASS Point
Source Catalog (PSC) entries in the vicinity of the position of interest.
You can do this with a simple position-radius search using
the IRSA GATOR tool. Find sources in the vicinity of your positions that
are detected in only 1 or 2 of the 3 2MASS bands (look at
the "rd_flg" values in the PSC entries: non-detected bands
are indicated with rd_flg="0" in the appropriate
digit). For the bands with non-detections, the quoted magnitudes
are 97% confidence upper brightness limits that were determined
by placing an aperture down on the non-compressed Atlas Image
at the source position and measuring the signal and noise.
You should be able to measure a characteristic
upper limit for each band from the sources around your position.
You can then quote these as approximate upper limits for your
sources.
The pixel values for the Atlas Images are in data-number units ("DN").
To convert to a calibrated mag, you need the zero point
mag given in the image header. Look for the keyword "MAGZP".
It is then straightforward to compute the calibrated mag:
mag = MAGZP - 2.5 log10 (flux),
where the flux is the integrated flux in "DN".
If you are referring to the extended source "postage stamp"
images (not yet available for the All-Sky Release),
then you need to look for the header keywords:
"JMAGZP", "HMAGZP" and "KMAGZP", for the J, H and Ks bands
respectively.
A word of warning: You should not use the compressed,
QuickLook images, available from the Quicklook Image Tool on IRSA.
These have been lossy compressed, so for point sources, the accuracy
of the photometry is, at best, ~10%. You should not attempt isophotal
photometry on extended sources at all for these Images.
(The following information applied to the Second Incremental Data Release
Catalogs. It may be now out-of-date for the All-Sky Data Release.)
The NED identifiers extracted
for 2MASS extended sources are unfortunately truncated at 9 characters during
pipeline processing, so the full names are not available. We would have to
run a query against NED to recover the identifiers, which is something
that you can actually do yourself. Fortunately, NED is doing
the matching for us all.
If you go to the "By Parameters" selection under "OBJECTS"
on the main NED web site,
you will see that it is now possible to select NED holdings
according to source name prefix. Thus, you can select the 2MASS prefix,
and Submit the Query, to obtain listing for the 2MASS XSC objects in NED.
These are:
For more information see Section VI.4a of the
All-Sky Data Release Explanatory Suppement.
This was the case up until 2002. We are very happy to report
that with the ROSS 2002 announcement, 2MASS is now a fully supported
data set for ADP and LTSA archival research proposals and is
not treated like external ground-based data.
This will also be true for future NRA's.
The
2MASS All-Sky Data Release took place on 25 March 2003.
All Atlas Image and Catalog data are available on-line.
Using GATOR at IRSA,
"jdate" (which is the Julian date for that observation, ±30 sec)
is part of the "standard" format of available Point Source Catalog
columns that can be selected
for your table output. Another column, "date" (which is the UT date of
the morning that an observation is completed), can be selected as part of
the "long form" format for available columns.
The answer to your question is very simple: the table is loaded into the
IRSA database, which will not accept file names that begin with a number.
The
2MASS All-Sky Point Source Catalog Statistics Service is now
available on-line through the
Infrared Science Archive (IRSA).
This tool can be used to estimate quickly the 2MASS PSC source number
count and color distributions in a specified circular region of the sky
without having to run a more time-consuming query on the full PSC.
The wording in the Explanatory Supplement and in the Extended Source Catalog
column descriptions for this parameter is not quite accurate.
The half-light surface brightness refers to the mean flux within the
half-light (effective) radius.
In other words, it is the mean surface brightness, which
is also known as the effective surface brightness.
Band
Lambda (µm)
Bandwidth (µm)
Fnu - 0 mag (Jy)
Flambda - 0 mag (W cm-2 µm-1)
J
1.235 ± 0.006
0.162 ± 0.001
1594 ± 27.8
3.129E-13 ± 5.464E-15
H
1.662 ± 0.009
0.251 ± 0.002
1024 ± 20.0
1.133E-13 ± 2.212E-15
Ks
2.159 ± 0.011
0.262 ± 0.002
666.7 ± 12.6
4.283E-14 ± 8.053E-16
Last update: 2006 February 1, 2MASS Helpdesk.
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