J/A+A/467/1003 Photometry of star clusters in NGC 1380 (Chies-Santos+ 2007)
High resolution imaging of the early type galaxy NGC 1380: an insight into
the nature of extended star clusters
Chies-Santos A.L., Santiago B.X., Pastoriza M.G.
<Astron. Astrophys. 467, 1003 (2007)>
=2007A&A...467.1003C 2007A&A...467.1003C
ADC_Keywords: Galaxies, photometry ; Photometry, UBV ; Morphology
Keywords: galaxies: individual: NGC 1380 - galaxies: star clusters
Description:
NGC 1380 is a lenticular galaxy located near the center of the Fornax
Cluster, northeast of NGC 1399. The globular cluster system of this
galaxy was previously studied only from the ground. Recent studies of
similar early-type galaxies, specially lenticular ones, reveal the
existence of star clusters that apparently break up the traditional
open/globular cluster dichotomy.
With higher quality photometry from HST/WFPC2 we study the star
clusters in NGC 1380, measuring their magnitudes, colours, sizes
and projected distances from the center of the galaxy.
We used deep archival HST/WFPC2 in the B and V bands. We built colour
magnitude diagrams from which we selected a sample of cluster
candidates. We also analysed their colour distribution and measured
their sizes. Based on their location in the luminosity-size diagram
we estimated probabilities of them being typical globular clusters
as those found in the Galaxy.
A total of about 570 cluster candidates were found down to V=26.5.
We measured sizes for approximately 200 of them. The observed colour
distribution has three apparent peaks. Likewise for the size
distribution. We identified the smaller population as being mainly
typical globular clusters, while the more extended objects have small
probabilities of being such objects. Different correlations between
absolute magnitudes, sizes, colours and location were inferred for
these cluster sub-populations.
Most extended clusters (Reff>4pc) share similar properties to the
diffuse star clusters reported to inhabit luminous early-type galaxies
in the Virgo galaxy cluster such as being of low surface brightness
and fainter than MV~-8. We also report on a small group of
(Reff∼10pc), -8<MV←6, red clusters located near the centre of
NGC 1380, which may be interpreted as faint fuzzies.
Description:
Table 4 contains positions and photometry for the resolved sample of
star clusters, i.e that we could measure sizes and which have
Reff<15pc.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 84 187 *Positions and photometry for the resolved
cluster sample
--------------------------------------------------------------------------------
Note on table4.dat: Objects identified as
[CSP2007] DD.ddddddd+DD.ddddddd in Simbad
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Chip [1,4] HST/WFPC2 chip number
3- 9 F7.3 pix Xpos X CCD coordinate
11- 17 F7.3 pix Ypos Y CCD coordinate
19- 28 F10.7 deg RAdeg Right Ascension J2000, in decimal degrees
30- 40 F11.7 deg DEdeg Declination J2000, in decimal degrees
42- 47 F6.3 mag Vmag Johnson V magnitude
49- 53 F5.3 mag e_Vmag Mean error on Vmag
55- 60 F6.3 mag Bmag Johnson B magnitude
62- 66 F5.3 mag e_Bmag Mean error on Bmag
68- 72 F5.3 mag B-V Johnson B-V colour index
74- 78 F5.2 pc Reff Effective radius of the cluster (1)
80- 84 F5.2 pc e_Reff Mean error on Reff
--------------------------------------------------------------------------------
Note (1): We adopted a distance modulus of (m-M)=31.4.
--------------------------------------------------------------------------------
Acknowledgements:
Ana Leonor Chies Santiago Santos, ana.leonor(at)ufrgs.br
(End) Patricia Vannier [CDS] 02-Mar-2007