J/MNRAS/452/3508 Young stellar structures in NGC 6503 (Gouliermis+, 2015)
Hierarchical star formation across the ring galaxy NGC 6503.
Gouliermis D.A., Thilker D., Elmegreen B.G., Elmegreen D.M., Calzetti D.,
Lee J.C., Adamo A., Aloisi A., Cignoni M., Cook D.O., Dale D.A.,
Gallagher J.S.III, Grasha K., Grebel E.K., Davo A.H., Hunter D.A.,
Johnson K.E., Kim H., Nair P., Nota A., Pellerin A., Ryon J., Sabbi E.,
Sacchi E., Smith L.J., Tosi M., Ubeda L., Whitmore B.
<Mon. Not. R. Astron. Soc., 452, 3508-3528 (2015)>
=2015MNRAS.452.3508G 2015MNRAS.452.3508G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Associations, stellar ; Morphology ;
Photometry, HST
Keywords: methods: statistical - stars: formation -
galaxies: individual: NGC 6503 -
galaxies: spiral - galaxies: stellar content - galaxies: structure
Abstract:
We present a detailed clustering analysis of the young stellar
population across the star-forming ring galaxy NGC 6503, based on the
deep Hubble Space Telescope photometry obtained with the Legacy
ExtraGalactic UV Survey. We apply a contour-based map analysis
technique and identify in the stellar surface density map 244 distinct
star-forming structures at various levels of significance. These
stellar complexes are found to be organized in a hierarchical fashion
with 95 percent being members of three dominant super-structures
located along the star-forming ring. The size distribution of the
identified structures and the correlation between their radii and
numbers of stellar members show power-law behaviours, as expected from
scale-free processes. The self-similar distribution of young stars is
further quantified from their autocorrelation function, with a fractal
dimension of ∼1.7 for length-scales between ∼20pc and 2.5kpc. The
young stellar radial distribution sets the extent of the star-forming
ring at radial distances between 1 and 2.5kpc. About 60 percent of
the young stars belong to the detected stellar structures, while the
remaining stars are distributed among the complexes, still inside the
ring of the galaxy. The analysis of the time-dependent clustering of
young populations shows a significant change from a more clustered to
a more distributed behaviour in a time-scale of ∼60Myr. The observed
hierarchy in stellar clustering is consistent with star formation
being regulated by turbulence across the ring. The rotational velocity
difference between the edges of the ring suggests shear as the driving
mechanism for this process. Our findings reveal the interesting case
of an inner ring forming stars in a hierarchical fashion.
Description:
LEGUS is an HST panchromatic stellar survey of 50 nearby star-forming
dwarf and spiral galaxies with an emphasis on UV-enabled science
applications. Images in a wide waveband coverage from the near-UV
(NUV) to the I band are being collected with WFC3 and ACS in parallel,
and combined with archival optical ACS data. The survey, its
scientific objectives and the data reduction are described in Calzetti
et al. (2015AJ....149...51C 2015AJ....149...51C).
We present a detailed clustering analysis of the young blue stellar
population identified with LEGUS across the star-forming ring galaxy
NGC 6503. We construct stellar surface density maps and apply a
contour-based analysis technique to identify the stellar complexes'
population of the galaxy. We identify 244 distinct structures at
various stellar density (significance) levels.
The complete catalogue of 244 structures is available online at LEGUS
site https://legus.stsci.edu/.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 80 244 Survey of the young stellar structures in NGC 6503
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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- 3 I3 --- ID ID number
5- 6 I2 --- Level Detection density threshold (in σ)
8- 17 F10.6 deg RAdeg Structure barycenter right ascension (J2000)
19- 27 F9.6 deg DEdeg Structure barycenter declination (J2000)
29- 32 I4 --- Nstars Number of the blue stars included within the
borders of every structure
34- 39 F6.1 pc reff Effective radius (size of each system) (1)
41- 46 F6.1 pc rmax Maximum radius (2)
48- 52 F5.3 --- elong [0.7/2.5] Elongation (rmax/reff)
54- 57 F4.2 10+3pc-2 SurfDens Surface stellar density (in 10-3stars/pc2)
59- 63 F5.2 mag UVmag Total F275W magnitude
65- 69 F5.2 mag umag Total F336W magnitude
71- 75 F5.2 mag bmag Total F438W magnitude
77 I1 --- Fam Family identification number
79- 80 I2 --- Group Group identification number
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Note (1): effective radius or equivalent radius, defined as the radius of a
circle with the same area as the area covered by the system. We provide two
measurements for this radius: the radius determined by the area ACH enclosed
by the convex hull of the system (reff=sqrt(ACH/π)).
Note (2): radius defined by the area Amax enclosed by the largest circle that
encompasses the entire system (rmax=sqrt(Amax/π)).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 11-Mar-2016