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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(unpublished, 1993; revised 2009)>
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:
FileName Lrecl Records Explanations
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
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.
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
Bytes Format Units Label Explanations
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 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)
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
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
Bytes Format Units Label Explanations
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
Note (1): the symbol refers to the survey: B = Bordeaux (2006A&A...448.1235D, Cat. I/300) D = DENIS (1999A&A...349..236E, Cat. B/denis) G = GSC-ACT (1999yCat.1255.....G, Cat. I/255) g = GSC-2.2 (2001yCat.1271.....S, Cat. I/271) I = IRAS (1988IRASP.C......0J, Cat. II/125) M = 2MASS (2003yCat.2246.....C, Cat. II/246) T = Tycho-2 (2000A&A...357..367H, Cat. I/259) U = UCAC2 (2004AJ....127.3043Z, Cat. I/289) X = MSX6C (2001AJ....121.2819P, Cat. V/114) s = Brian Skiff's estimate
Byte-by-byte Description of file: ps_id.dat
Bytes Format Units Label Explanations
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
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
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