VI CCD Photometry of HST images of NGC 346

1
VI CCD Photometry of HST images of NGC 346
Supervisor Prof. Isabella Pagano Prof. Ana I
Gomez de Castro
Investigator Saurabh Snehlata (ARIES, INDIA)
2
Star Cluster
Gravitationally bound group of stars which formed
from same molecular cloud at same time and
located at same distance Importance To
understand the stellar evolution and star
formation
Scientific objectives

• To examine the colour magnitude diagram of star
  cluster,
• To derive its fundamental parameters like
  distance, age and reddening,
• To study mass function of cluster

3
Observations and Data reduction

• NGC 346, SMC cluster, was observed with Wide
  field Channel (WFC) of Advanced Camera for
  Surveys (ACS).
• Filters F555W (V) and F814W (I),
• Pipeline reduced FITS files from the HST data
  archive.
• Ran multidrizzle, created drizzled image, useful
  to generate a deep image
• Photometry IRAF/DAOPHOT package.
• Photometric calibrations according to Srianni et
  al.(2005).

4
SMC cluster NGC 346 Distance of SMC 60 Kpc
5
Colour-Magnitude diagram
Age10 Myr
m-M18.85
Age4.5 Gyr
(m-M)18.85 mag
E(B-V)0.013 mag
E(B-V)0.01 mag
Girardi et al. (2002)
6
Mixed population
Image taken by HST/ACS and circles represent
different regions of different type of population
Old population
Young population
7
Statistical subtraction
Central region
Field region
Young pop.
Northern region
Field region
Old pop.
8
Field substracted CMD
Young population
Old population
9
Mass Function
? -2.11 0.40
? -2.28 0.59
?-2.210.50
MF for old stars in the mass range 1.1-1.2 Solar
Mass. Error bar represents vN
MF for PMS (young population) in the mass range
1.5-7 Solar Mass. Error bar represents vN
10
Results

• Distance of the N346 is found to be
  58Kpc
• We have Identified mixed population in
  the CMD of the cluster region
• Younger population shows a spread in the
  age from 5 to 10 Myr. The age of the older
  population comes out to be 4.5 Gyrs.
• The mass function slope for younger
  population (-2.21-0.51) in the mass
  range 1.5-7 Solar is steeper then Salpeter
  Value (-1.35).
• The mass function for older population
  in the mass range 1.1-1.2 Solar mass is
  found to be almost flat

11
Thanks