Fourteen-color Photometry of M13 and Ruprecht 8 using the Dichroic-Mirror Camera (DMC)

Transcription

1 Fourteen-color Photometry of M13 and Ruprecht 8 using the Dichroic-Mirror Camera (DMC) MASTER S THESIS A manuscript written as one requirement to obtain Master s degree from Institut Teknologi Bandung Written by HANINDYO KUNCARAYAKTI NIM : GRADUATE PROGRAM OF ASTRONOMY FACULTY OF MATHEMATICS AND NATURAL SCIENCES INSTITUT TEKNOLOGI BANDUNG 2008

2 i APPROVAL PAGE Fourteen-color photometry of M13 and Ruprecht 8 using the Dichroic-Mirror Camera (DMC) Written by Hanindyo Kuncarayakti NIM : Graduate Program of Astronomy Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung Approved by Bandung, 24 June 2008 Supervisor I, Supervisor II, Dr. Hakim Luthfi Malasan Prof. Mamoru Doi (NIP ) (Institute of Astronomy, Graduate School of Science, the University of Tokyo)

3 ii Abstract Photometry has been carried out to the globular cluster M13 and open cluster Ruprecht 8 (Ru 8) using the Dichroic-Mirror Camera (DMC). DMC is an instrument developed at the Institute of Astronomy, the University of Tokyo, which has the capability of simultaneous imaging in 15 colors across nm. Observation has been carried out in Higashi-Hiroshima Observatory using the 1.5-m Kanata telescope on 7 March Due to some problem, the observation was done in 14 colors. The raw images obtained during the observation was reduced and measured by employing PSF and aperture photometry. Instrumental magnitudes derived from the measurement were calibrated into standard magnitudes. The resulting photometric sequence was used to generate cluster colormagnitude diagram (CMD) and spectral energy distribution (SED) of its member stars. Theoretical isochrones were then fitted to the data scatter in the CMD. The best-fit isochrones yielded physical parameters of the clusters, i.e. T = 18.0 Gyr, [Fe/H] = 1.67, (m 4 M 4 ) = 14.9, E(m 4 m 11 ) = 0.0, d = 9.5 kpc for M13 and T = Myr, [Fe/H] = 0.76, (m 4 M 4 ) = 11.54, E(m 4 m 12 ) = 1.05, d = 800 pc for Ru 8. These results, however, do not agree perfectly with the references. Future improvements in data analysis and possibly the instrument itself are suggested to refine current results.

4 iii ACKNOWLEDEGMENTS It would be impossible to me to work on this topic without my two supervisors, Dr. Hakim L. Malasan and Prof. Mamoru Doi. I hereby would like to gratefully appreciate them for their supports and guidance. Also I would like to thank the referees, Drs. S.D. Wiramihardja, M. Raharto, and M.I. Arifyanto for important suggestions in improving this work. I also would like to acknowledge the DMC team for their help and supports. Financial support from the ITB Voucher Scholarship is gratefully acknowledged. I am thankful to my teachers and colleagues with whom I shared fruitful discussions and for their encouragements. I would also like to thank Dr. Jan-Uwe Ness (School of Earth and Space Exploration, Arizona State University) for his help in working with L A TEX. This work has made use of NASA s Astrophysics Data System Bibliographic Services, SIMBAD database, operated in CDS, Strasbourg, France, and WEBDA database, operated at the Institute for Astronomy of the University of Vienna.

5 Contents Contents List of Figures List of Tables v viii x 1 Introduction Background Summary Hypothesis Methods Chapter outlines Literature study Description of the instrument Description of the objects M Ruprecht Data acquisition and pre-process The Observation The Data Bias images Dark images Flat images Examination of data images Reduction process Data analysis: photometric reductions Introduction to photometry Standard star photometry HD iv

6 CONTENTS v BD HZ HD Cluster photometry Ru M Calibration to standard magnitudes Zero-point shift Photometric transformation equations Data analysis: CMD and SED Astrometric reduction CMD fitting CMD of M13 and Ru Constructing isochrones in DMC bands Isochrone fitting SED fitting Discussions & summary 78 Bibliography 87 A Report of visit to Japan 88 A.1 Results of the visit A.1.1 Week I: 24 Feb - 1 Mar A.1.2 Week II: 2 Mar - 9 Mar A.1.3 Week III: 10 Mar - 16 Mar A.1.4 Week IV: 17 Mar - 21 Mar A.2 Follow-up and future prospects B Photometric sequence 94 C Finding charts 104

7 List of Figures 2.1 Some of the DMC dichroic mirrors Throughput of 15 DMC bands Inside of DMC The 14 effective DMC bands The DMC attached to Kanata telescope CCD dewar temperature variations CCD dewar pressure variations Variations of dome (black) and outside (cyan) temperatures Example of normal bias image Histogram of a bias image, central portion Subtraction results: sub1 (left) and sub2 (right) Contour of bias image Pressure change in bias from CCD # Fitting the dark-reference region Example of bias image with strong noise, DMC DMC after dark-reference correction Example of normal dark frame, DMC (60s) Example of dark-reference and bias-corrected dark frame Example of skyflat image Example of clean skyflat image DMC , after reduction Distribution of images in the UT-P plane Example of bias image pair with strong noise Example of a bad flat image due to star contamination Topology diagram of TC-215 chip A slice along column and line of a sample flat image A sample of raw bias image from CCD # Example of negative bias and dark image with their contours Example of object images Image DMC fits vi

8 LIST OF FIGURES vii 4.2 Instrumental magnitude of HD Image DMC fits Instrumental magnitude of BD Image DMC fits. HZ44 is marked with green circle Instrumental magnitude of HZ Image DMC fits Instrumental magnitude of HD Ru 8 in band #1 (421 nm), and band #11 (772 nm) An example of daofind detection Plot of magnitude vs. error Plot of variation of chi and sharpess An example of M13 images Plot of magnitude vs. error Plot of variation of chi and sharpess for M SED of BD SED of four standard stars SED of four standard stars SED of four standard stars Coordinates for Ru 8 (left) and M13 (right) stars Sample CMD for M13 (left) and Ru 8 (right) CMD for M13 from different fileds Comparison between DMC and UBVRI system Synthesized photometry for BVRI and DMC Transformation from V to DMC# Transformation from BRI bands to each DMC analog Transformation from BVRI colors to each DMC analog Isochrone in V(B-V) (left) and DMC analog (right) CMD of M13, from zero-point shift CMD of M13, from transformation Preliminary CMD fit of M Selection of isochrones of different ages; z = Selection of isochrones of different metallicity; T = 15 Gyr M13, final isochrone fit Ru 8 CMD, m 4 (m 4 m 11 ) Transformation from (V I) into (m 4 m 12 ) Final isochrone fit for Ru SED of several M13 stars SED of several Ru 8 stars M13, final isochrone fit

9 LIST OF FIGURES viii 6.2 Final isochrone fit for Ru Heliocentric XYZ coordinates Galactic metallicity gradient A.1 GAO 150 cm telescope C.1 Finding chart of M13 (north), from ALADIN C.2 Finding chart of M13 (east), from ALADIN C.3 Finding chart of M13 (south), from ALADIN C.4 Finding chart of M13 (west), from ALADIN C.5 Finding chart of Ru 8, from ALADIN

10 List of Tables 2.1 Physical parameters of M Physical parameters of Ru Correspondence between CCD and passband ID Observed objects on 7 Mar Bias image statistics Experimental bias image statistics dark-reference fitting result Dark image statistics, 60s exposure Flat image statistics, 20s exposure Flat image statistics, 20s exposure Bias image statistics, one set Bias image statistics, CCD # Dark image statistics Statistics of combined bias Statistics of combined dark Statistics of combined flat Object list Example of image statistics Zero point from HZ Solved variables Solved variables, equation set Parameters of M Parameters of Ru A.1 Timetable of future plan B.1 Photometric sequence of Ruprecht 8, for band B.2 Photometric sequence of Ruprecht 8, for band B.3 Photometric sequence of M13, for band 1 7, star ix

11 LIST OF TABLES x B.4 Photometric sequence of M13, for band 1 7, star B.5 Photometric sequence of M13, for band 1 7, star B.6 Photometric sequence of M13, for band 1 7, star B.7 Photometric sequence of M13, for band 1 7, star B.8 Photometric sequence of M13, for band 8 14, star B.9 Photometric sequence of M13, for band 8 14, star B.10 Photometric sequence of M13, for band 8 14, star B.11 Photometric sequence of M13, for band 8 14, star