J/AJ/138/1037 Star formation in Centaurus A Group dwarfs (Cote+ 2009)
Star formation in dwarf galaxies of the nearby Centaurus A Group.
Cote S., Draginda A., Skillman E.D., Miller B.W.
<Astron. J., 138, 1037-1061 (2009)>
=2009AJ....138.1037C 2009AJ....138.1037C
ADC_Keywords: Galaxies, optical ; H II regions ; Photometry, H-alpha
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: irregular -
H II regions
Abstract:
We present Hα narrow-band imaging of 17 dwarf irregular (dI)
galaxies in the nearby Centaurus A Group. Although all large galaxies
of the group are or recently have been through a period of enhanced
star formation, the dIs have normal star formation rates (SFRs) and do
not contain a larger fraction of dwarf starbursts than other nearby
groups such as the Sculptor Group or the Local Group. Most of the
galaxies in the group now have fairly accurately known distances,
which enables us to obtain relative distances between dIs and larger
galaxies of the group. We find four transition dwarfs in the Group,
dwarfs that show characteristics of both dE/dSphs and dIs, and which
contain cold gas but no current star formation.
Description:
We observed all of the 19 dwarf irregular (dI) galaxy members of the
Centaurus A Group listed in Cote et al. (1997AJ....114.1313C 1997AJ....114.1313C). Of
these, 17 were detected and are listed in Table 1. The Hα
images, were obtained with the Cerro Tololo Inter-American Observatory
(CTIO) 0.9m telescope over 8 nights in 1999 April. The observations
usually consisted of 3x1200s through a narrow-band Hα filter
centered at 6559Å and with a FWHM of 64Å, followed by a 2x1200s
for continuum off-band images through a filter centered at 6115Å
and with a FWHM of 140Å. R-band images were also acquired.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 17 Centaurus A Group dwarf irregular (dI) galaxies
detected in Hα
table2.dat 63 22 Star formation properties of Centaurus A Group dI
galaxies
table3.dat 56 282 HII regions positions and Hα fluxes
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See also:
J/AJ/133/504 : Galaxies around CenA/M83 galaxy complex (Karachentsev+, 2007)
J/MNRAS/346/787 : HIDEEP survey (Minchin+, 2003)
J/A+AS/141/469 : First list of the Karachentsev catalog (Huchtmeier+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Galaxy name
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 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- 37 I3 km/s HV Heliocentric velocity from Cote et al.,
1997AJ....114.1313C 1997AJ....114.1313C
39- 42 F4.2 Mpc Dist Distance
44- 47 F4.2 Mpc e_Dist ? Distance uncertainty
49 I1 --- r_Dist [1/2]? Dist reference (1)
51- 56 F6.2 mag BMag Absolute B-band magnitude
58- 61 F4.2 mag e_BMag BMag uncertainty
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Note (1): Distances from reference as follows:
1 = Karachentsev et al. (2007, Cat. J/AJ/133/504);
2 = Karachentsev et al. (2002A&A...385...21K 2002A&A...385...21K)
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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- 12 A12 --- Name Galaxy name
13 A1 --- n_Name [cde] Notes (2)
15- 20 E6.2 Msun/yr SFR Total star formation rate (3)
22- 28 E7.2 Msun/yr/Lsun SFR/LB SFR normalized to the galaxy luminosity
30- 35 F6.1 Gyr tForm Estimated star formation timescale
37 A1 --- l_MHI Limit flag on MHI
38- 42 F5.1 10+6Msun MHI Total galaxy HI mass (M(HI)) (4)
44 A1 --- l_MHI/LB Limit flag on MHI/LB
45- 48 F4.2 Msun/Lsun MHI/LB Gas mass normalized to the galaxy
luminosity
50 A1 --- l_tGas Limit flag on tGas
51- 56 F6.1 Gyr tGas Gas depletion timescale (5)
58- 63 F6.2 Msun/yr/pc2 SFR/area ? SFR per unit area
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Note (2): Flag as follows:
c = From Bouchard et al. 2009AJ....137.3038B 2009AJ....137.3038B.
d = Hα data from Phillips et al. (1986AJ.....91.1062P 1986AJ.....91.1062P), HI mass from
Banks et al. (1999ApJ...524..612B 1999ApJ...524..612B), using the nominal distance of 3.8Mpc.
e = Hα data from Bouchard et al. (2009AJ....137.3038B 2009AJ....137.3038B), HI mass from
Beaulieu et al. (2006AJ....131..325B 2006AJ....131..325B), using a distance of 4.23Mpc from
Jerjen (2000AJ....119..166J 2000AJ....119..166J).
Note (3): The SFRs were calculated using Equation (1) with Hα luminosities
obtained by summing all the HII region luminosities listed in Table 3.
Equation 1 : SFR(total)=(L(Hα)/(1.26x1041erg/s))M☉/yr
Note (4): Total galaxy HI mass from Cote et al., 1997AJ....114.1313C 1997AJ....114.1313C,
adjusted to the distance in Table 1.
Note (5): τgas is the gas depletion timescale =(Total Gas Mass)/(SFR),
where the total gas mass is 1.32xM(HI) to account for He.
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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- 12 A12 --- Name Galaxy name
14- 15 I2 --- Num HII region number
17- 18 I2 h RAh Hour of right ascension (J2000)
20- 21 I2 min RAm Minute of right ascension (J2000)
23- 27 F5.2 s RAs Second of right ascension (J2000)
29 A1 --- DE- Sign of declination (J2000)
30- 31 I2 deg DEd Degree of declination (J2000)
33- 34 I2 arcmin DEm Arcminute of declination (J2000)
36- 39 F4.1 arcsec DEs Arcsecond of declination (J2000)
41- 46 F6.1 aW/m2 FHa Hα flux in 10-15erg/cm2/s
48- 51 F4.1 aW/m2 e_FHa FHa uncertainty
53- 56 F4.1 [10-7W] logLHa Log of Hα luminosity in erg/s
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Nomenclature Notes:
In table 3, HII regions are <[CDS2009] {Name} NN> in Simbad.
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 20-Jan-2012