J/ApJ/353/494 JHKL photometry on Galactic bulge M Giants (Frogel+, 1990)
Galactic bulge M Giants. II. Content and structure of the bulge between
b = -3 and -12
Frogel J.A., Terndrup D.M., Blanco V.M., Whitford A.E.
<Astrophys. J. 353, 494 (1990)>
=1990ApJ...353..494F 1990ApJ...353..494F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Photometry, infrared
Keywords: galaxies: stellar content - galaxies: The Galaxy - photometry -
stars: abundances - stars: late-type - stars: long-period variables
Abstract:
JHKL colors and CO and H2O indices are presented for an unbiased
sample of about 250 M giants drawn from complete surveys for such
stars along the minor axis of the Galaxy at latitudes between -3deg
and -12deg. Magnitudes at 10 µm and narrow-band near-infrared
colors for some of these stars are also given.
At constant J-K the mean CO index of the bulge M giants weakens
monotonically with increasing latitude. From the relation between CO
and [Fe/H] established for star clusters, this would correspond to a
decrease of ∼0.4 dex in the mean [Fe/H] between the -3deg and -12deg
fields, from somewhat greater to somewhat less than solar. These
values are consistent with abundances derived from optical
color-magnitude diagrams. Despite these high [Fe/H] values, the
ridgelines of the color-magnitude diagrams for all fields lie between
those of 47 Tucanae and M3. There is a mild blueward shift with
increasing latitude seen in the integrated mean J-K colors of the
fields. A steady progression with latitude in the mean (J-H, H-K)
relation for the bulge M giants is observed.
For the -12deg field it is significantly displaced from the one for
local field giants and overlaps that for globular cluster stars; for
the -3deg field it is displaced by about the same amount, but on the
opposite side of the field giant relation. Dispersions about this
relation and the mean (CO, J-K) relation for the M giants in each
field are comparable in size to the measuring uncertainties alone, but
in a given field the displacements of individual stars from these two
mean relations are statistically correlated. We attribute this
correlation to a spread in metallicity within each field but note that
this spread is smaller than the total metallicity range over all
fields. In addition, metallicity-related effects result in J-H getting
bluer with increasing metallicity in stars of similar temperature.
The bolometric luminosity function of the nonvariable M giants is
nearly independent of latitude. All show a sharp cutoff at Mbol≤-4.2;
such a cutoff could be a good extragalactic distance indicator for
bulgelike stellar populations. The reddest (J-K≥-1.35) and most
luminous stars are found only in the low-latitude windows; all are
M7-M9 giants, long-period variables (LPVs), or both. Except for these
reddest stars, the ratio at a given color of M7-M9 giants to earlier
type giants is independent of latitude. Only when stars of all colors
in a spectral group are considered is the rapid falloff seen in the
ratio of M7-M9 giants respect to earlier types. The bulge LPVs have
<Mbol> = -4.2. Since this is nearly the same as for LPVs in globular
clusters, it does not require an age for the bulge population
significantly younger than that of globular clusters. Their spatial
distribution is similar to that of the reddest late M giants. The LPVs
with the reddest colors, attributed to the most extensive
circumstellar dust shells, are found in the lowest latitude fields.
Most of the bulge IRAS sources in the fields studied can be identified
with these LPVs or with the brightest nonvariable M giants; many of
the latter are probably foreground objects. The reddest IRAS sources
are at the lowest latitudes and have the coolest [12-25]µm colors.
The bulge IRAS sources do not appear to represent a different or more
luminous class of objects than the optically identified M giants. Five
different estimators of the surface brightness and surface density
between latitudes -3deg and -12deg have a power-law dependence on
radius with exponent between -2.5 and -3.4. The value of the exponent
depends on the metallicity of the estimator: the most metal-rich
objects have the steepest falloff. However, even the smallest
exponent, which characterizes the total light and mass distribution,
places the bulge among the most spatially concentrated of those
measured by Kent for a sample of 22 Sb-Sc galaxies. Thus the mass
distribution within the inner 1.5 kpc of the Galaxy is quite sharply
peaked.
See also:
GCPD/66 : General Catalog of Photometric Data, system #66
(CO,H2O, 2.36um and 2.0um intermediate-band filters)
J/AJ/110/2788 : JHK photometry for Galactic bulge stars (Tiede+ 1995)
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 99 39 Reddening-corrected photometry for at b=-3deg
table3.dat 107 51 Reddening-corrected photometry for at b=-6deg
table4.dat 107 91 Reddening-corrected photometry for at b=-8deg
table5.dat 75 47 Reddening-corrected photometry for at b=-10deg
table6.dat 107 55 Reddening-corrected photometry for at b=-12deg
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Byte-by-byte Description of file: table2.dat table3.dat table4.dat table5.dat table6.dat
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Bytes Format Units Label Explanations
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2- 8 A7 --- Star Star
9 A1 --- n_Star [f] When 'f' = field stars (they have not
been reddening-corrected)
11 I1 --- SpBin ? Spectral bin (1)
12 A1 --- n_SpBin [VC?] When 'V'= variable,
'C' = carbon star, '?' = unknown
14- 18 F5.2 mag Kmag K magnitude
21 I1 cmag e_Kmag ? Error on K magnitude (3)
27- 31 F5.2 mag Mbol ? Bolometric magnitude
34- 37 F4.2 mag J-K J-K colour index
40 I1 cmag e_J-K ? Error on J-K (3)
44- 48 F5.2 mag H-K H-K colour index
51 I1 cmag e_H-K ? Error on H-K (3)
53- 56 F4.2 mag K-L ? K-L colour index
59 I1 cmag e_K-L ? Error on K-L (3)
61- 65 F5.2 mag H2O ? H2O index
68 I1 cmag e_H2O ? Error on H2O index (3)
70- 75 F6.3 mag CO ? CO index (from 2.29 µm band)
78 I1 cmag e_CO ? Error on CO index (3)
81- 84 F4.2 mag K-[10] ? K-[10] index
87- 88 I2 cmag e_K-[10] ? Error on K-[10] (3)
95- 99 F5.3 mag 102-C220 ? 102-C220 colour
101-107 A7 --- Notes Notes (2)
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Note (1): the spectral bin has the values
2 = M2-M4
5 = M5-M6
7 = M7-M9
Note (2): the numbers are those assigned
by Plaut (1971A&AS....4...75P 1971A&AS....4...75P) and
by Blanco (1987AJ.....93..321B 1987AJ.....93..321B);
When 'IRAS' = stars identified with IRAS sources
Note (3): The uncertainties are only shown if equal or greater than
0.03mag in JHK, CO, H2O, 0.04mag in K-L, and 0.06mag in K-[10].
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Historical Notes: Keypunched at CDS
(End) Simona Mei [CDS] 31-Aug-1995