CCD photometry of Large Magellanic Cloud clusters. I. Theremote cluster NGC 1777.
Abstract
Photographic (B and V) and CCD (B, V, and R) photometry of stars in the remote LMC cluster NGC 1777, and integrated UBV photometry of the inner part of the cluster are presented. A comparison of the results from the two techniques revealed large (about 0.2 mag) systematic differences which were attributed to the difficulty of faint photographic photometry. The photographic calibration depended on images produced by a Racine wedge, while the CCD calibration was accomplished in a manner analogous to photoelectric photometry. The stellar photometry provides a C-M diagram to V equal to about 21.5 which includes an evolved main sequence and a well-populated giant branch. A variety of methods, including comparisons of the observations to two sets of isochrones, allows us to estimate the cluster age as 0.9 + -0.2 x 10 to the 9th years. However, we are only able to estimate the metallicity (Fe/H) crudely as -0.7 + or - 0.5. The C-M diagrams of the field in three regions near NGC 1777 indicate the presence of stars in the age range 1 x 10 to the 9th to less than or equal to 3 x 10 to the 9th years although we are unable to discern whether a mixture of two or more distinct populations or a continuous distribution of field-star ages is responsible for this spread.
- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- September 1985
- DOI:
- 10.1086/131602
- Bibcode:
- 1985PASP...97..753M
- Keywords:
-
- Astronomical Photometry;
- Charge Coupled Devices;
- Magellanic Clouds;
- Star Clusters;
- Color-Magnitude Diagram;
- Histograms;
- Metallicity;
- Stellar Luminosity;
- Tables (Data);
- Astrophysics