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J/AJ/110/1649        VI photometry near the M33 nucleus (Mighell+ 1995)

Hubble Space Telescope Planetary Camera observations of the stellar populations near the nucleus of M33 Mighell K.J., Rich R.M. <Astron. J. 110, 1649 (1995)> =1995AJ....110.1649M
ADC_Keywords: Populations, stellar ; Photometry Abstract: We have studied the stellar populations near the nucleus of the nearby spiral galaxy M33 using archival observations of the Hubble Space Telescope Planetary Camera in the F555W and F785LP passbands. The I vs (V-I) color-magnitude diagram reveals a young stellar population with a blue main sequence and red supergiants, and stars in a blue loop that are Cepheid candidates. An old red giant branch is clearly visible, with a break at I=20.7mag which is, within the observational errors, identical to the giant branch termination point of the Mould & Kristian (1986ApJ...305..591M) halo field. However, red giants are seen up to I=19.5mag, and many bright red giants are undetected in the V band. We find evidence for a wide abundance spread of at least 1.5dex from metal-poor (∼M15) to metal-rich (≥47Tucanae) in the Population II stars, in sharp contrast to the M33 halo field of Mould & Kristian (1986ApJ...305..591M) which is metal-poor (∼M92) with a narrow abundance range. We show that the various stellar populations have different spatial distributions. The Population II stars are more centrally concentrated than the Population I stars. The red giants brighter than I=20.7 (the termination point for a Galactic globular cluster giant branch) are found to be more centrally concentrated than the (presumably) old red giants. The most-centrally concentrated bright Population II giants are probably associated with the many bright red giants that are undetected in the V band. These infrared-bright giants were probably created in an intermediate-age burst of star formation that took place well after the formation of the oldest halo stars but long before the recent burst of star formation seen in nearby OB associations. This stellar population probably corresponds to the bulge identified in the infrared H band by Minniti et al. (1993ApJ...410L..79M). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 70 4077 Photometry of stars near the nucleus of M33 2880 60 FITS BINTABLE version of table 1
See also: J/AJ/121/861 : BVI photometry of central part of M33 (Macri+, 2001) J/AJ/121/870 : Variables in the central part of M33 BVI phot. (Macri+, 2001) J/A+A/366/498 : HST VI photometry of M33 star clusters (Chandar+, 2001) J/AJ/110/2715 : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
2- 10 I9 --- ID Coded identification (1) 12- 18 F7.2 mag F785LP F785LP (i) magnitude 20- 24 F5.2 mag e_F785LP F785LP photometric error 26- 32 F7.2 mag F555W F555W (v) magnitude 34- 38 F5.2 mag e_F555W F555W photometric error 40- 45 F6.2 mag Imag []?=99.99 I magnitude 47- 51 F5.2 mag V-I V-I color 53- 59 F7.2 arcsec dRA Right ascension (J2000) offset (2) 61- 67 F7.2 arcsec dDE Declination (J2000) offset (2) 69- 70 I2 --- Class Photometric measurement class (3)
Note (1): The left-most digit of the ID gives the PC chip number where the star may be found (5, 6, 7, or 8). The right-most 4 digits of the ID gives the x coordinate of the star multiplied by 10. The remaining 4 digits gives the y coordinate of the star multiplied by 10. All positions are given with respect to the W0M00104T data set. For example, the first star in Table 1 has an ID of 505142912 which indicates that it has the (x,y) position of (291.2, 51.4) on the PC5 CCD of the W0M00104T data set. Note (2): Offsets in arcseconds from the nucleus of M33 (ID = 634043615) for the standard HST epoch of J2000.0. Note (3): 1 = v and i photometry (2532 stars) 2 = only i photometry (1028 stars) 3 = only v photometry (517 stars)
Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 31-Oct-1995
(End) [CDS] 25-Jan-1996
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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