III/170B IRAS Point Source Identifications (MacConnell, 1993; rev. 2009)
IRAS Point Sources of flux at 12 microns greater than flux at 25 microns and
falling within about 7 degrees of the Galactic Plane
MacConnell D. J.
<(unpublished, 1993; revised 2009)>
=1993yCat.3170.....M 1993yCat.3170.....M
ADC_Keywords: Infrared sources ; Stars, late-type ; Cross identifications
Abstract:
The file "ps_class.dat" is an ASCII text file containing the
classifications of 14,192 IRAS Point Sources with the flux at 12µm
greater than the flux at 25µm and falling within about 7° of
the galactic plane. The aim has been to provide classifications of
IRAS-PS with no previous associations, so most bright stars such as in
the BSC, SAO, and HD which have associations and good spectral types
are not included. Also, many known carbon stars from the catalogue of
Stephenson known to be associated with PS are not included.
Introduction:
Most of the sources are south of the celestial equator and have been
classified in increasing galactic longitude over the period Sept. 1985
to May 1992. They have been classified on Kodak I-N objective-prism
plates taken primarily with the Curtis Schmidt telescope at Cerro
Tololo, but some northern plates taken with the Burrell Schmidt at
Kitt Peak were also used for classification. The spectra cover the
range 680-880nm at a dispersion of 340nm/mm at the A-band, and the
plate scale is 96.6"/mm. They are ideal for classifying M stars of
type M3 and cooler (increasing strength of TiO and VO bands) and
carbon stars (CN bands), but stars warmer than M2 and most S stars
cannot be classified or identified as such. The M stars M3 and cooler
can be separated into about five groups. The limiting mag of the
deepest plates is I about 13.5.
The IRAS PS were identified on transparent overlays made to the plate
scale for each plate center, and the association of a spectrum with
a given PS is usually unambiguous. In cases of doubt or offset, a
comment is made. Note that there are some cases where the PSC gives an
incorrect association on the basis of position, and the correct
association is with a faint, uncatalogued M star.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ps_class.dat 72 14189 The catalog of identifications, 2009 Version
ps_id.dat 69 14192 The catalog of identifications, 1994 version
mac_iras.dat 139 13099 *Cross-identifications and remarks by B. Skiff
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Note on mac_iras.dat: this addition does not include the stars originally
marked '<M', i.e. earlier than type M; see more details in the
"Introduction to mac_iras" section below.
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See also:
II/125 : IRAS catalogue of Point Sources, Version 2.0 (IPAC 1986)
III/36 : General catalogue of cool carbon stars (GCCCS, Stephenson 1973)
III/156 : Cool Galactic Carbon Stars, 2nd Edition (GCCGC, Stephenson 1989)
III/227 : General Catalog of galactic Carbon stars, 3d Ed. (Alksnis+ 2001)
Byte-by-byte Description of file: ps_class.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- IRAS IRAS-PSC Name (Cat. II/125)
12- 36 A25 --- Class Classification of the star and comments
(<M means "M2 or earlier")
37- 40 F4.1 arcsec Off ? Offset from IRAS position
41- 42 A2 --- Dir [NSEW ] Direction of offset from IRAS position
43- 47 I5 --- Plate Plate number
48- 48 A1 --- n_Plate [lms] Note on Exposure/Plate (1)
49- 50 I2 --- den [0,20]? Density on a scale of 0 to 20
51 A1 --- u_den [:?v] Uncertainty flag (:) on den
52- 72 A21 --- Remarks Cross-identifications and remarks (2)
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Note (1): Plate/exposure are coded as:
l = 60min exposure, sensitized plate
m = 30min exposure
s = 5min exposure
Note (2): Not all variable stars, carbon stars, etc. have been identified
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Introduction to mac_iras file (by B. Skiff, July 2005):
The principal value in MacConnell's list is to provide precise
coordinates for the IRAS sources, often for the first time, along
with external IDs in the visible and near-IR, and the spectral
classifications. MacConnell occasionally classified companion red
stars in the near fields of the IRAS sources. In addition, MacConnell
has been very kind to re-examine many ambiguous cases on his plate
collection, and has provided new or revised types for red stars.
The variety of remarkable objects in this list is fascinating.
By way of background, the IRAS spacecraft made the first complete
sky survey in the mid-infrared about 1983. Among the products was a
catalogue of some third of a million sources that seemed unresolved
at the rather poor resolution of the detector system. Objects were
detected as they passed across a bunch of slits placed over the
detectors (the pattern of the slit-mask looked something like a
cheese-grater). Thus the positions were determined from when the
source passed over successive holes in the mask together with
knowledge of the spacecraft pointing and spin motion. The resulting
positions have an uncertainty expressed as an oval, typically about
40"-60" long and 10"-20" wide, often aligned approximately east-west.
Dominating the detections close to the Milky Way are red stars. These
appear bright due to circumstellar dust whose output peaks at around
10µm wavelength. (The stars themselves peak at 1-2µm) One of the
four filters on IRAS was a very wide passband centered near 12µm
that (very conveniently) takes in most of this 10µm emission from
the envelopes around cool stars. In most instances IRAS detected the
stars in the 12µm band, sometimes very weakly at 25µm, and not
at all at two longer wavelengths. This pattern is usually enough to
separate the red stars from other things detected by IRAS.
Now, Jack MacConnell has made a career of doing surveys on objective-
prism plates taken mostly with the Curtis Schmidt at Cerro Tololo in
Chile. Among these was a large series of plates covering the southern
galactic plane in the photographic infrared, what we would now call
the 'far-red', spanning most of the Cousins R and I photometric
passbands. The broad molecular bands appearing in the spectra of cool
stars makes them easy to identify on such plates. So while looking for
stars of more immediate interest (carbon and the rare S-type stars),
he also inventoried the ubiquitous M-giants appearing at the locations
of IRAS sources. To some extent this helped answer the question (at
the time) of what all these IRAS sources were that seemed to have no
catalogued visible counterpart. (Answer: a plethora of cool late-M
giants obscured by interstellar or circumstellar dust, or both.)
With this as background, I've started to chip away at the 14,000
object list to make it more usable. I proceeded as follows. Taking the
IRAS names in batches of 50 or 100, I first used VizieR to look for
'best' coordinates, which came mostly from UCAC2 (Cat. I/289) or 2MASS
(Cat. II/246). UCAC2 is the current state-of-the-art among astrometric
star catalogues, and the positions are mostly better than 0".1
accuracy. The 2MASS catalogue resulted from a survey in the three
near-IR photometric bands J, H, and K (about 1.2, 1.6 and 2.2 µm).
Red stars, even if very faint in the visible are booming bright, even
overexposed in the K band. This is because the dimming caused by
interstellar extinction is reduced by a factor of ten at K compared
to the visual.
The key element was to find the brightest 'very red' 2MASS source
within or near the IRAS position error-ellipse. Recall that these are
95-percent confidence-intervals for the source position. I usually
used a 45arcsec search radius in VizieR. Note that an unreddened M0
giant has J-K ∼1.0, so the stars always were very much redder in the
2MASS data and generally very much brighter than anything else in the
field. Nearly always this search yielded a single unambiguous red star
consistent with MacConnell's classification. If the star was not
present in UCAC2 I usually reverted to the 2MASS coordinates (mostly
good to < 0".2), but sometimes used other sources if the 2MASS
detection was overexposed. Bill Gray's GSC-ACT (Cat. I/255) still
comes in handy.
Where MacConnell found a 'blank field' or only faint non-banded stars
I tried to ascertain why. I sought red stars in 2MASS well outside the
nominal position error limits, and also looked in the MSX catalogue
(Cat. V/114). MSX is another near/mid-infrared survey done as part of
a military project to map the background sky at wavelengths relevant
to detection of ballistic missiles ('Star Wars' stuff). It included
several wavelength bands, but the only really sensitive one was
centered at about 8µm, again with a wide passband taking in that
10µm glow from the cool stars as does IRAS. MSX is about a factor
of five more sensitive than IRAS at this wavelength, and the
coordinates for sources have errors of typically only a few arcsec
(versus a few tens of arcsec for IRAS). As with the other catalogues
mentioned, it is on-line and very easily searchable using the
Strasbourg VizieR utility.
In many instances the red star was simply outside the IRAS error
ellipse, and Jack said he kept pretty strictly within that boundary
for the classifications. In other cases it was clear that the red star
was simply too faint. I presumed the limit of his far-red plates was
in the magnitude range 11 < Ic < 13 depending on things like crowding
or overlapping of the spectral images, plate flaws, and perhaps star
color. Rough I-band magnitudes could be found from the USNO-B1.0
catalogue (Cat. I/284) or from DENIS (Cat. B/denis), both also
available through VizieR searches. A few obscured objects were below
this limit in the 2MASS J band (but bright at K and the MSX 8µ band)
so obviously these were just too faint in the visible, even at I.
Another class of 'blank fields' is for IRAS sources that are not red
stars. MacConnell's selection was simply that the IRAS 12µm flux is
greater than the 25µm flux. But this is insufficient to eliminate
things like deeply-embedded hot stars, various sorts of nebulae
(planetary, circumstellar shells around hot stars, HII regions), or
even galaxies. A look at the complete IRAS fluxes in the SIMBAD
headers was usually enough to decide this. Where neither 2MASS nor
the MSX catalogue showed a red star, I revert to the original IRAS
coordinates (sometimes improved from MSX) and leave the rest of the
entry blank. Whatever solution was found to these special cases is
given in the notes. Rather than try to determine the type of object
(it is often indeterminate), I simply remark "not a red star". I might
note that I often used DSS and 2MASS images from the Goddard SkyView
utility to help sort out identifications in crowded fields.
While getting coordinates I also got at least a rough estimate of the
V magnitude for each object. Some of these are good means from ASAS-3
or TASS MkIV, and even Tycho-2, but others are just averages of the
GSC-2.2 and USNO-B1.0 red and blue magnitudes. Every star of course is
at least somewhat variable, so any of these are merely indicative. As
an aside, it is quite interesting too look up the ASAS lightcurves for
a bunch of these to see the variety of forms they exhibit.
Once accurate coordinates were determined, I ran the corrected
positions (again in batches) into VizieR looking at the GSC and MSX6C
catalogue and copy those names as available. The MSX survey covers
only the narrow strip within a few degrees of the galactic plane
(usually out to ± 3°, but out to 7° in a few places).
I decided to show one "common" external identifier if this was
available, and thus also searched the HD/HDE, BD/CD/CPD, Dearborn red
stars, GCVS v4.1 (and now v4.2), and CGCS3. I used 3' search radii in
VizieR for all these except the Dearborn catalogue, whose soft
coordinates require a 5' search radius. Among the carbon stars I show
the CGCS name in preference to the GCVS, but retain HD/BD names over
all others. Finally, I searched every star in SIMBAD using a 3' search
radius. The main result of all this was many dozens of IDs for fusion
in SIMBAD, which I have bombarded upon Gerard Jasniewicz (the official
SIMBAD database fixer at that time) in the form of a long string of
e-mail lists; it'll take him awhile to get all that cleaned up.
Byte-by-byte Description of file: mac_iras.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- IRAS IRAS-PSC Name (Cat. II/125)
12 A1 --- f_IRAS [*!] additional note in file notes.htx (*),
or the optical source differs from IRAS (!)
14- 15 I2 h RAh Right Ascension J2000 (hours)
17- 18 I2 min RAm Right Ascension J2000 (minutes)
20- 24 F5.2 s RAs Right Ascension J2000 (seconds)
26 A1 --- DE- Declination J2000 (sign)
27- 28 I2 deg DEd Declination J2000 (degrees)
30- 31 I2 arcmin DEm Declination J2000 (minutes)
33- 36 F4.1 arcsec DEs Declination J2000 (seconds)
38 A1 --- r [BDGgIMTUXs] Origin of position (1)
40- 48 A9 --- GSC GSC designation (Cat. I/254)
50- 66 A17 --- MSX6C Designation in MSX6C (Cat. V/114)
68- 71 F4.1 mag Vmag ? Visual magnitude (indicative)
74- 80 A7 --- Sp Spectral class
81 A1 --- n_Sp [r] 'r' for spectrum significantly reddened
83-139 A57 --- Remarks Cross-identifications and remarks
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Note (1): the symbol refers to the survey:
B = Bordeaux (2006A&A...448.1235D 2006A&A...448.1235D, Cat. I/300)
D = DENIS (1999A&A...349..236E 1999A&A...349..236E, Cat. B/denis)
G = GSC-ACT (1999yCat.1255.....G 1999yCat.1255.....G, Cat. I/255)
g = GSC-2.2 (2001yCat.1271.....S 2001yCat.1271.....S, Cat. I/271)
I = IRAS (1988IRASP.C......0J 1988IRASP.C......0J, Cat. II/125)
M = 2MASS (2003yCat.2246.....C 2003yCat.2246.....C, Cat. II/246)
T = Tycho-2 (2000A&A...357..367H 2000A&A...357..367H, Cat. I/259)
U = UCAC2 (2004AJ....127.3043Z 2004AJ....127.3043Z, Cat. I/289)
X = MSX6C (2001AJ....121.2819P 2001AJ....121.2819P, Cat. V/114)
s = Brian Skiff's estimate
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Byte-by-byte Description of the file: ps_id.dat
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Bytes Format Units Label Explanation
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1-10 A10 --- IRAS IRAS Name
11-35 A25 --- class Classification
36-41 A6 arcsec off [NSEW ".0-9]Offset from IRAS position
42-46 I5 --- Npl Plate number
47-48 A2 --- NplS Plate number supplement
49-50 A2 --- den Density on a scale of 0 to 20
51-69 A19 --- id Identifications / remarks
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Acknowledgements:
This work has been supported by the NASA ADP during several cycles,
and further funding will be sought to continue classifying beyond
the current cut-off in gal. longitude of 314 deg. If there are
comments/corrections/ questions, please contact:
D. Jack MacConnell
CSC/STScI Tel.: 410-338-4800
3700 San Martin Drive FAX: 410-338-4767
Baltimore, MD 21218
History:
* 02-May-1994: Original version, prepared by
Nancy G. Roman [NASA/NSSDC/ADC] and
D. Jack MacConnell [STScI]
* 27-Jul-2009: Revised version prepared by D. Jack MacConnell,
as well as comments by B. Skiff from 2007 (Lowell Obs.).
About 50 IRAS names corrected to be consistent with IRAS-PSC.
* 26-Aug-2010: file "mac_iras.dat" which contains most of the
original IRAS sources studied by B. Skiff, has been added.
(End) D. Jack MacConnell [STScI], Francois Ochsenbein [CDS] 26-Aug-2010