J/ApJ/298/544 NGC 121 BR photometry (Stryker+ 1985)
The main-sequence turnoff of the old SMC globular cluster NGC 121
Stryker L.L., Da Costa G.S., Mould J.R.
<Astrophys. J. 298, 544 (1985)>
=1985ApJ...298..544S 1985ApJ...298..544S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Photometry, CCD
Keywords: clusters: globular - galaxies: Magellanic Clouds - stars: abundances -
stars: evolution
Abstract:
The age of the SMC globular cluster NGC 121 is found from
main-sequence isochrone fitting to be 12±2x109yr if a distance
modulus that assumes Mv=+0.6 for the field RR Lyrae variables near
the cluster is used. If instead (m-M)o = 19.3, then the cluster age is
9±2x109yr. The cluster is known to contain both RR Lyrae
variables and a marginal carbon star; comparison with theoretical
models indicates no significant inconsistencies in this joint
occurrence at either modulus. The color-magnitude diagram for the
nearby field also shows a faint, blue main-sequence turnoff and, in
contrast to previous Magellanic Cloud field studies, the field lacks
any evidence for the existence of a significant intermediate-age
component. A new look at the chemical evolution of the Small
Magellanic Cloud suggests that, unlike the Galaxy, where the rate of
enrichment has been steady after the initial phase, the enrichment in
the SMC remained small for a long interval before increasing rapidly
sometime in the last 1-2x109yr.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
00 26.7 -71 31 NGC 121
-----------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1 40 242 Photometry in NGC 121
table2 42 300 Photometry in field
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1 table2
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Star Star identification number
5- 8 F4.2 mag B-R B-R color index
10- 14 F5.2 mag Rmag R magnitude
16- 21 F6.2 pix Xpos X position (1)
23- 28 F6.2 pix Ypos Y position (1)
30- 34 F5.2 mag DB-R ? November 18-20 B-R color index difference
36- 40 F5.2 mag DRmag ? November 18-20 R magnitude difference
--------------------------------------------------------------------------------
Note (1): Origin: southwest corner of fig. 1
--------------------------------------------------------------------------------
History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 30-Sep-1996