J/AJ/138/1203 Star formation regions in nearby dwarf galaxies (Melena+, 2009)
Bright ultraviolet regions and star formation characteristics in nearby dwarf
galaxies
Melena N.W., Elmegreen B.G., Hunter D.A., Zernow L.
<Astron. J. 138, 1203 (2009)>
=2009AJ....138.1203M 2009AJ....138.1203M
ADC_Keywords: Galaxies, nearby ; Ultraviolet ; Photometry, UBV
Keywords: galaxies: dwarf - galaxies: irregular - galaxies: star clusters
Abstract:
We compare star formation in the inner and outer disks of 11 dwarf
irregular galaxies (dIm) within 3.6Mpc. The regions are identified on
Galaxy Evolution Explorer near-UV images, and modeled with UV,
optical, and near-IR colors to determine masses and ages. A few
galaxies have made 105-106M☉ complexes in a starburst phase,
while others have not formed clusters in the last 50Myr. The maximum
region mass correlates with the number of regions as expected from the
size-of-sample effect. We find no radial gradients in region masses
and ages, even beyond the realm of Hα emission, although there
is an exponential decrease in the luminosity density and number
density of the regions with radius. Hα is apparently lacking in
the outer parts only because nebular emission around massive stars is
too faint to see. The outermost regions for the five galaxies with HI
data formed at average gas surface densities of 1.9-5.9M_☉/pc2.
Description:
In this paper, we compare the properties of individual star-forming
regions in outer and inner disks of a sample of dwarf galaxies. The
young regions are identified on Galaxy Evolution Explorer (GALEX)
near-UV (NUV) images archives. We use far-UV (FUV) and NUV, UBV, and
some JHK colors to model the masses and ages of the regions. Our
investigation includes approximately 2000 separate star-forming
regions. With these data we compare mass, age, and several other key
properties of star-forming regions in inner and outer disks.
GALEX images were taken simultaneously in two channels: FUV, with a
bandpass of 1350-1750Å, an effective wavelength of 1516Å, and a
resolution of 4.0" and NUV with a bandpass of 1750-2800Å, an
effective wavelength of 2267Å, and a resolution of 5.6".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 11 Galaxy sample
table3.dat 119 1622 Region photometry
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See also:
J/A+A/495/447 : PN and HII regions in NGC6822 (Hernandez-Martinez+, 2009)
J/ApJ/706/599 : Hα and UV SFR in the local volume (Lee+, 2009)
J/ApJS/162/49 : UBV imaging of irregular galaxies (Hunter+, 2006)
J/AJ/132/378 : HST and UV photometry of NGC 6822 (Bianchi+, 2006)
J/AJ/121/2020 : CTIO and WFPC2 photometry in NGC 6822 (Bianchi+, 2001)
J/AJ/105/894 : Star formation in DDO 210 and NGC 3109 (Greggio+ 1993)
J/A+AS/125/293 : NGC 2366, NGC 2403 + NGC 4236 HK' photometry (Pierini+ 1997)
J/AJ/110/2715 : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995)
J/AJ/109/173 : BVR photometry of NGC 6822 (Marconi+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Galaxy name (1)
10- 54 A45 --- OName Other name(s)
56- 58 F3.1 Mpc Dist Distance
60- 63 F4.2 mag E(B-V) Foreground reddening from Burstein & Heiles,
1984ApJS...54...33B 1984ApJS...54...33B
65- 69 F5.1 mag VMag Absolute V-band magnitude
71- 74 F4.2 arcmin RD ? Disk scale length determined from V-band images
76- 78 I3 deg PA [-85,88] Galactic position angle of the major
axis determined from V-band images
80- 81 I2 deg i Inclination of galactic disk
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Note (1): Quantities taken from Hunter & Elmegreen (2006, Cat. J/ApJS/162/49).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Galaxy name
10- 12 I3 --- Reg Star-forming region number
14- 15 I2 h RAh Hour of Right Ascension (J2000)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 23 F4.1 s RAs Second of Right Ascension (J2000)
25 A1 --- DE- Sign of the Declination (J2000)
26- 27 I2 deg DEd Degree of Declination (J2000)
29- 30 I2 arcmin DEm Arcminute of Declination (J2000)
32- 33 I2 arcsec DEs Arcsecond of Declination (J2000)
35- 38 F4.2 kpc R Distance from galaxy center (1)
40- 44 F5.2 --- R/RD Same as R but divided by disk scale length (2)
46- 50 F5.1 pc radius Star-forming region radius (3)
52- 56 F5.1 mag NUVMag Absolute GALEX NUV filter AB magnitude
58- 61 F4.2 mag e_NUVMag The 1σ error in NUVMag
63- 67 F5.2 mag F-N Intrinsic GALEX (FUV-NUV) color index
69- 72 F4.2 mag e_F-N The 1σ error in F-N
74- 78 F5.1 mag VMag Absolute V filter AB magnitude
80- 82 F3.1 mag e_VMag The 1σ error in VMag
84- 88 F5.2 mag B-V Intrinsic (B-V) color index
90- 93 F4.2 mag e_B-V The 1σ error in B-V
95- 99 F5.2 mag U-B Intrinsic (U-B) color index
101-104 F4.2 mag e_U-B The 1σ error in U-B
106-109 F4.2 [Msun] logM Log star-forming region mass (4)
111-114 F4.2 [yr] logA Log star-forming region age (4)
116-119 F4.2 mag RMS rms deviation between observed & modeled colors
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Note (1): In the plane of the galaxy, using the galactic parameters given
in Table 1.
Note (2): From Hunter & Elmegreen (2006, Cat. J/ApJS/162/49).
Note (3): The identifying regions are polygons, and the radius is the
square-root of the area of the region divided by π.
Note (4): From the best fit model to the colors and luminosity.
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Nomenclature Notes:
Regions are <[MEH2009] {Name} NNN> in Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 23-Jan-2012