J/A+A/594/A34 Young star groups in NGC 300 (Rodriguez+, 2016)
Detailed photometric analysis of young star groups in the galaxy NGC 300.
Rodriguez M.J., Baume G., Feinstein C.
<Astron. Astrophys. 594, A34 (2016)>
=2016A&A...594A..34R 2016A&A...594A..34R (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar; Clusters, open ; Stars, early-type
Keywords: stars: luminosity function, mass function -
galaxies: individual: NGC 300 - galaxies: star clusters: general -
galaxies: star formation
Abstract:
The purpose of this work is to understand the global characteristics
of the stellar populations in NGC 300. In particular, we focused our
attention on searching young star groups and study their hierarchical
organization. The proximity and orientation of this Sculptor Group
galaxy make it an ideal candidate for this study.
The research was conducted using archival point spread function (PSF)
fitting photometry measured from images in multiple bands obtained
with the Advanced Camera for Surveys of the Hubble Space Telescope
(ACS/HST). Using the path linkage criterion (PLC), we cataloged young
star groups and analyzed them from the observation of individual stars
in the galaxy NGC 300. We also built stellar density maps from the
bluest stars and applied the SExtractor code to identify
overdensities. This method provided an additional tool for the
detection of young stellar structures. By plotting isocontours over
the density maps and comparing the two methods, we could infer and
delineate the hierarchical structure of the blue population in the
galaxy.
For each region of a detected young star group, we estimated the size
and derived the radial surface density profiles for stellar
populations of different color (blue and red). A statistical
decontamination of field stars was performed for each region. In this
way it was possible to build the color-magnitude diagrams (CMD) and
compare them with theoretical evolutionary models. We also constrained
the present-day mass function (PDMF) per group by estimating a value
for its slope.
The blue population distribution in NGC 300 clearly follows the spiral
arms of the galaxy, showing a hierarchical behavior in which the
larger and loosely distributed structures split into more compact and
denser ones over several density levels. We created a catalog of 1147
young star groups in six fields of the galaxy NGC 300, in which we
present their fundamental characteristics. The mean and the mode
radius values obtained from the size distribution are both 25pc, in
agreement with the value for the Local Group and nearby galaxies.
Additionally, we found an average PDMF slope that is compatible with
the Salpeter value.
Description:
Fundamental characteristics of 1147 young star groups identified in 6
ACS/WFC fields of the galaxy NGC 300.
For each group: field of the ACS/WFC, equatorial coordinates, radius,
number of stars (the suffix bri indicates bright stars with F555W<25,
the suffix dct indicate stars belonging to the decontaminated region,
the suffixes blue and red refer to blue and red stars respectively),
the magnitude of the brightest star in the group, PDMF slope with its
error, and galactocentric distance.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 95 1147 Characteristics of 1147 young star groups
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Name Identification number of the star group
(FNNN, where F is the ACS/WFC field number)
6 I1 --- Field [1/6] ACS/WFC field
8- 16 F9.6 deg RAdeg Right ascension (J2000.0)
18- 27 F10.6 deg DEdeg Declination (J2000.0)
29- 32 F4.2 arcsec Rad Radius
34- 37 I4 --- N Number of stars in the group's region
39- 42 I4 --- Nbri Number of stars with F555W<25
44- 47 I4 --- Ndct Number of stars after the decontamination
process
49- 52 I4 --- Ndct-bri Number of decontaminated stars with F555W<25
54- 57 I4 --- Nblue Number of blue stars
59- 62 I4 --- Nblue-dct Number of blue stars with F555W<25
64- 67 I4 --- Nred Number of red stars
69- 72 I4 --- Nred-dct Number of red stars with F555W<25
74- 78 F5.2 mag Magmin Magnitude of the brightest star in F555W band
80- 84 F5.2 --- PDMFslope ?=- Present day mass function slope
86- 90 F5.2 --- e_PDMFslope ?=- PDMF slope error
92- 95 F4.2 kpc dgc Galactocentric distance
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Acknowledgements:
Jimena Rodriguez, jimenaro(at)fcaglp.unlp.edu.ar
(End) Jimena Rodriguez [FCAGLP, La Plata], Patricia Vannier [CDS] 26-Aug-2016