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J/ApJ/470/864       JHKL photometry of the Galactic Center   (Blum+, 1996)

JHKL photometry and the K-band luminosity function at the Galactic Center. Blum R.D., Sellgren K., Depoy D.L. <Astrophys. J. 470, 864 (1996)> =1996ApJ...470..864B
ADC_Keywords: Associations, stellar ; Photometry, infrared ; Reddening Keywords: dust, extinction - Galaxy: center - Galaxy: stellar content - infrared: stars - stars: luminosity function, mass function Abstract: J, H, K, and L photometry for the stars in the central ∼2' (∼5pc) of the Galaxy are presented. Using the observed J-H, H-K, and K-L colors and assumed intrinsic colors, we determine the interstellar extinction at 2.2mm (AK) for approximately 1100 individual stars. The mean AK (=3.3mag) is similar to previous results, but we find that the reddening is highly variable, and some stars are likely to be seen through AK>6mag. The dereddened K-band luminosity function points to a significantly brighter component to the stellar population (>1.5mag at K) than found in the stellar population in Baade's window, confirming previous work done at lower spatial resolution. The observed flux of all Galactic center stars with estimated K0 (dereddened magnitude) =<7.0mag is ∼25% of the total in the 2'x2' field. The data were obtained in July 11-13 on the 4m telescope at the Cerro Tololo Observatory (CTIO) using the Ohio State Infrared Imager qnd Spectrometer (OSIRIS). Our observations confirm the recent finding that several bright M stars in the Galactic center are variable. Our photometry also establishes the near-infrared variability of the M1-2 supergiant, IRS 7. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 89 185 Galactic center observed photometry notes.dat 80 43 Notes to table1.dat table2.dat 83 12 Variable stars in the Galactic Center table4.dat 81 159 Galactic Center reddening-corrected photometry
See also: J/A+A/368/835 : Soft X-ray sources in the GC region (Sidoli+, 2001) J/A+A/373/608 : Early-type stars towards the GC. II. (Dufton+, 2001) J/A+AS/92/43 : Radio Obs. of OH/IR stars close to GC (Lindqvist+ 1992) J/A+AS/97/587 : JHK photometry of Galactic center stars (Ruelas-Mayorga+ 1993) J/A+AS/128/35 : New Sample of OH/IR stars in GC (Sjouwerman+ 1998) J/AJ/106/2291 : UBV photometry toward Galactic Center (Reed 1993) J/ApJ/523/248 : Variable stars in the Galactic center (Ott+, 1999) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [BSD96] Sequential number 4 A1 --- n_[BSD96] [*] *: variable star, in table2.dat file 6- 16 A11 --- Name Name (G1) 18- 23 F6.2 arcsec oRA Offset in right ascension from IRS 7 (2) 26- 31 F6.2 arcsec oDE Offset in declination from IRS 7 (2) 34- 38 F5.2 mag Kmag K magnitude (3) 40- 43 F4.2 mag e_Kmag rms uncertainty on Kmag 46- 49 F4.2 mag J-K ? J-K colour index (3) 51- 54 F4.2 mag e_J-K ? rms uncertainty on J-K 57- 60 F4.2 mag H-K ? H-K colour index (3) 62- 65 F4.2 mag e_H-K ? rms uncertainty on H-K 68- 71 F4.2 mag K-L ? K-L colour index (3) 73- 76 F4.2 mag e_K-L ? rms uncertainty on K-L 78- 89 A12 --- Notes Comma-separated notes, see file notes.dat
Note (2): IRS 7: RA = 17 45 39.987 DE = -29 00 22.24 ICRS 2000.0 (Position from Simbad, ref: 1989IAUS..136..443Y) Note (3): All photometry is from our primary OSIRIS data set unless otherwise noted. The OSIRIS magnitudes include both measurement and calibration uncertainties. The DePoy & Sharp (1991AJ....101.1324D, hereafter DS91) data include only measurement uncertainty; calibration uncertainty is not included.
Byte-by-byte Description of file: notes.dat
Bytes Format Units Label Explanations
1- 4 A4 --- Note Symbol used in table1 9- 80 A72 --- Text Text of note
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 7 A7 --- Name Star name (IRS 7, 9 and 12N) 9- 13 F5.2 mag Jmag ? J magnitude 15- 18 F4.2 mag e_Jmag ? rms uncertainty on Jmag 20- 24 F5.2 mag Hmag ? H magnitude 26- 29 F4.2 mag e_Hmag ? rms uncertainty on Hmag 31- 34 F4.2 mag Kmag ? K magnitude 36- 39 F4.2 mag e_Kmag ? rms uncertainty on Kmag 41- 44 I4 yr Obs.Y Observation date (year) 46- 52 A7 --- Obs.M Observation date (month/month) 54- 73 A20 --- Set Data set (1) 75- 83 A9 -- Filt Filters used to derive J, H, and K magnitudes (2)
Note (1): Data set: Becklin et al., 1978ApJ...220..831B DS91: DePoy & Sharp, 1991AJ....101.1324D DS91b: DS91 photometry is consistent with J, H, and K magnitudes of IRS 7 being the same as for Becklin et al., 1978ApJ...220..831B; see text. Note (2): J, H, and K are broad-band filters. KND is broad-band K with a 1% neutral density filter. NBK is K magnitude derived from two narrow-band filters (Δλ/λ=1%) near 2.2mm; see text.
Table 3: Young stellar object (YSO) photometry -------------------------------------------------------------------------------- Observed Reddened (Red) Reddened (Blue) Reference YSO name K H-K K H-K K H-K -------------------------------------------------------------------------------- CRL 2591 8.6 3.7 12.2 6.0 6.3 2.3 1976PASP...88..874M CRL 2059 8.7 2.6 12.3 4.9 8.2 2.3 1985ApJ...298..328S CRL 490 9.8 2.6 13.4 4.9 9.3 2.3 1976PASP...88..874M CRL 989 9.9 2.6 13.5 4.9 9.4 2.3 1972ApJ...172L..55A W33A 10.6 2.7 14.2 5.0 9.9 2.3 1987A&A...181..378C S140/IRS 1 10.7 2.4 14.3 4.7 10.5 2.3 1989ApJ...346..212E CRL 961 10.8 1.7 14.4 4.0 11.7 2.3 1985AJ.....90.1113C NGC 7538/IRS 9 10.9 5.8 14.5 8.1 5.3 2.3 1979MNRAS.188..463W Mon R2/IRS 3 11.2 3.0 14.8 5.3 10.0 2.3 1976ApJ...208..390B BN 11.2 4.6 14.8 6.9 7.5 2.3 1967ApJ...147..799B S255/IRS 1 11.6 2.2 15.2 4.5 11.7 2.3 1977ApJ...217..448E -------------------------------------------------------------------------------- Notes: Observed: observed K magnitude, corrected to a Galactic center (GC) distance of 8kpc, and observed H-K color of YSO. No correction has been applied for either the reddening of the YSO or the extinction toward the GC. Reddened (Red): Predicted K magnitude and H-K color of YSO at the GC, if the YSO is intrinsically red. This assumes the intrinsic H-K color of the YSO equals its observed H-K color, and there is no correction to the YSO for extinction in its surrounding molecular cloud. An average GC extinction of AK=3.6mag and E(H-K)=2.3mag has been applied. Reddened (Blue): Predicted K magnitude and H-K color of YSO at the GC, if the YSO is intrinsically blue. This assumes the intrinsic color of the YSO is H-K=0.0 and the observed H-K color of the YSO is used to correct for extinction in its surrounding molecular cloud. An average GC extinction of AK=3.6mag and E(H-K)=2.3mag has been applied. Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [BSD96] Sequential number 5- 15 A11 --- Name Name (G1) 16 A1 --- n_Name [*] Individual note on IRS 10EL (1) 18- 21 F4.2 mag K0mag Dereddened K magnitude (2) 23- 26 F4.2 mag e_K0mag rms uncertainty on K0mag 29- 32 F4.2 mag AK Absorption in K band (3) 34- 37 F4.2 mag e_AK ? rms uncertainty on AK 40- 43 F4.2 mag (J-K)0 ? Dereddened J-K colour index (2) 45- 48 F4.2 mag e_(J-K)0 ? rms uncertainty on (J-K)0 51- 54 F4.2 mag (H-K)0 ? Dereddened H-K colour index (2) 56- 59 F4.2 mag e_(H-K)0 ? rms uncertainty on (H-K)0 61- 65 F5.2 mag (K-L)0 ? Dereddened K-L colour index (2) 67- 70 F4.2 mag e_(K-L)0 ? rms uncertainty on (K-L)0 72- 81 A10 --- Notes Notes (4)
Note (1): See notes for Table 1. Since this star is variable and K and L were observed at different times, it is possible that the observed K-L is too red and AK overestimated. The source is probably quite red, however, since it was not detected at H or J. Note (2): Includes photometric uncertainty and uncertainty in derived AK. K0 results from average of DS91 and OSIRIS K when these differed by less than 0.2mag. Note (3): Includes photometric uncertainty only. No uncertainty given for the case of mean reddening (AK=3.58) or AK = lower limit; see notes c and d. For the case of two or more observed colors, only observed colors that fell within +0.5 mag of the reddening line were used to determine AK; see text. Note (4): Notes: c: AK is an estimated lower limit resulting from H-K, where H is taken as the limiting H magnitude (14.25); see text. d: Mean AK adopted from stars with measured H-K only; see text.
Global notes: Note (G1): Names: Simbad nomenclature when different than the written names: AF XXX: NAME AF XXX in Simbad BSD WC9, F95, TAM He1: Tam GCHe1 in Simbad IRS: <GCIRS NNWA>, <GCIRS NNA> (Nos 2L, 6WB, 10EL, 12NB, 30B) IRS "A" names are taken from Tamura et al. (1996ApJ...467..645T). Label "B" refers to a (usually) fainter source very close to the primary source. Earlier, lower resolution data likely included both components as a single source. F95 (not in Simbad) refers to sources observed by Figer (1995, Ph. D. thesis, UCLA).
History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 25-Jun-2001
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