J/AJ/97/1360 BV photometry of Palomar 12 (Stetson+ 1989)
CCD photometry of the anomalous globular cluster Palomar 12
Stetson P.B., Vandenberg D.A., Bolte M., Hesser J.E., Smith G.H.
<Astron. J. 97, 1360 (1989)>
=1989AJ.....97.1360S 1989AJ.....97.1360S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry, CCD
Abstract:
We present broadband B,V photometry for 1154 stars in the field of the
Galactic globular cluster Palomar 12, based upon direct CCD images
obtained with the Canada-France-Hawaii 3.6m and Cerro Tololo 4m
telescopes. The overall zero points of our V magnitudes and B-V colors
appear to be known to about ±0.02mag and ±0.01mag, and our
magnitude- and color-scale errors are probably controlled to <0.01mag.
Pal 12's main sequence shows an excess fringe of stars along its red
edge which are probably binaries; the CM diagram also contains a small
number of probable blue stragglers. The principal result of this paper
is that the color-magnitude diagram of Pal 12 is anomalous, in the
sense that we cannot fake all of its principal sequences lie near or
between those of the well studied and presumably typical Galactic
globular clusters 47 Tucanae and M5, even though it lies near or
between them in overall heavy-element abundance. The simplest
explanation is that Pal 12 is younger than the other two clusters by
some 25-30%. Other explanations are also possible, although perhaps
somewhat harder to believe. This result greatly strengthens the
possibility that age differences are responsible, at least in part,
for the anomalous properties of some of the outer-halo globular
clusters. Spectroscopic indications are that Pal 12's chemical
abundances should also strongly resemble those of the two Galactic
globular clusters NGC 288 and NGC 362, which have also been claimed to
show age differences in comparison with M5. However, attempts to
derive ages for these clusters relative to M5 and Pal 12 are
inconclusive, possibly due to some inconsistencies within the
available data.
Objects:
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RA (2000) DE Designation(s)
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21 46.5 -21 14 Palomar 12 = C 2143-214
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3 82 1154 Photometry for stars in Pal 12.
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Star number (1)
6- 11 F6.2 pix Xpos X position (2)
13- 19 F7.2 pix Ypos Y position (2)
21- 26 F6.3 mag Vmag V magnitude
28- 32 F5.3 mag e_Vmag rms uncertainty on Vmag
34- 39 F6.3 mag B-V B-V colour index
41- 45 F5.3 mag e_B-V rms uncertainty on B-V
47- 48 I2 --- o_Vmag Number of observation in Vmag (3)
50- 51 I2 --- o_Bmag Number of observation in Bmag (3)
53- 56 F4.2 --- <Chi> Mean of the goodness of fit index
58- 62 F5.2 pix Mean of the image radius index (4)
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Note (1): ID < 5000: stars measured by Harris et Canterna (1980ApJ...239..815H 1980ApJ...239..815H)
ID > 5000: Object not measured by Harris et Canterna (1980)
Note (2): X increasing from South to North, Y increasing from West to East
1 pix = 0.20"
Note (3): Total number of frames in each pass-band in which the star
was measurable.
Note (4): Positive when an object appears to be more extended than the
model stellar profile for the frame
Negative when the detection appears sharper than a star image
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History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 05-May-1997