2002A&A...393..461P


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.02CET02:54:13

2002A&A...393..461P - Astronomy and Astrophysics, volume 393, 461-483 (2002/10-2)

The blue compact dwarf galaxy I Zw 18: A comparative study of its low-surface-brightness component.

PAPADEROS P., IZOTOV Y.I., THUAN T.X., NOESKE K.G., FRICKE K.J., GUSEVA N.G. and GREEN R.F.

Abstract (from CDS):

Using HST and ground-based optical and NIR imaging data, we investigate whether the blue compact dwarf (BCD) galaxy I Zw 18 possesses an extended low-surface-brightness (LSB) old stellar population underlying its star-forming regions, as is the case in the majority of BCDs. This question is central to the long-standing debate on the evolutionary state of I Zw 18. We show that the exponential intensity decrease observed in the filamentary LSB envelope of the BCD out to >18" (>1.3kpc assuming a distance of 15Mpc) is not due to an evolved stellar disc underlying its star-forming regions, but rather, due to extended ionized gas emission. Ionized gas accounts for more than 80% of the line-of-sight emission at a galactocentric distance of ∼0.65kpc (∼3 effective radii), and for >30% to 50% of the R light of the main body of I Zw 18. Broad-band images reveal, after subtraction of nebular line emission, a relatively smooth stellar host extending slightly beyond the star-forming regions. This unresolved stellar component, though very compact, is not exceptional for intrinsically faint dwarfs with respect to its structural properties. However, being blue over a radius range of ∼5 exponential scale lengths and showing little colour contrast to the star-forming regions, it differs strikingly from the red LSB host of standard BCDs. This fact, together with the comparably blue colours of the faint C component, ∼1.6kpc away from the main body of I Zw 18, suggests that the formation of I Zw 18 as a whole has occurred within the last 0.5Gyr, making it a young BCD candidate. Furthermore, we show that the ionized envelope of I Zw 18 is not exceptional among star-forming dwarf galaxies, neither by its exponential intensity fall-off nor by its scale length. However, contrary to evolved BCDs, the stellar LSB component of I Zw 18 is much more compact than the ionized gas envelope. In the absence of an appreciable underlying stellar population, extended ionized gas emission dominates in the outer parts of I Zw 18, mimicking an exponential stellar disc on optical surface brightness profiles.

Abstract Copyright:

Journal keyword(s): galaxies: dwarf - galaxies: formation - galaxies: evolution - galaxies: structure - galaxies: starburst - galaxies: individual (I Zw 18, II Zw 70, III Zw 102, VII Zw 403, Tol 3, Henize 2-10, IC 4662, Mkn 36, Mkn 71, Mkn 178, Mkn 314, Mkn 324, Mkn 600, NGC 1705, NGC 1800, NGC 5253)

Simbad objects: 43

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Number of rows : 43

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 QSO B0125-0635 QSO 01 27 35.5241670251 -06 19 35.428005150 14.75 15.05 14.48 14.06 13.70 ~ 91 0
2 NGC 1036 G 02 40 28.982 +19 17 49.48   13.5       ~ 109 0
3 Mrk 600 G 02 51 04.57 +04 27 13.9 14.76 15.07 14.70 14.50 14.29 ~ 117 0
4 SBSG 0335-052 bCG 03 37 44.04 -05 02 38.5     16.65     ~ 438 1
5 NGC 1569 IG 04 30 49.186 +64 50 52.52 11.72 11.86 11.03     ~ 1167 3
6 NGC 1705 SBG 04 54 13.500 -53 21 39.82 12.32 12.96 12.56 12.58 12.9 ~ 604 1
7 NGC 1800 G 05 06 25.737 -31 57 15.21 13.51 13.19 12.70 12.48 12.9 ~ 161 1
8 Mrk 5 H2G 06 42 15.9 +75 37 40   17.0       ~ 109 0
9 NGC 2363A HII 07 28 42.8 +69 11 21           ~ 543 3
10 NGC 2366 H2G 07 28 51.85 +69 12 31.1 12.25 11.86 11.39 11.33   ~ 711 0
11 NGC 2537 IG 08 13 14.643 +45 59 23.25 12.18 12.50 11.69 11.66   ~ 275 1
12 LEDA 2790884 bCG 08 25 55.521 +35 32 31.96   18.2       ~ 106 1
13 ESO 495-21 bCG 08 36 15.190 -26 24 33.66 12.04 11.93 11.45 11.09 12.3 ~ 512 3
14 UGC 4483 GiG 08 37 03.29 +69 46 29.2 15.70 15.46 14.98 14.89   ~ 272 0
15 NAME Zwicky's Flare HII 09 34 00.0 +55 14 25           ~ 21 0
16 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 1014 1
17 Mrk 116B EmG 09 34 02.389 +55 14 23.14           ~ 50 0
18 LEDA 27886 QSO 09 44 17.101 +54 11 28.83   19.5       ~ 65 0
19 UGC 5272 B G 09 50 19.484 +31 27 22.22   17.53       ~ 29 0
20 NGC 3125 H2G 10 06 33.318 -29 56 07.32 13.03 13.45 13.00 12.50 13.4 ~ 217 1
21 NAME Leo I dSph G 10 08 28.12 +12 18 23.4   11.3 10.0     ~ 1077 1
22 Mrk 33 IG 10 32 31.956 +54 24 03.53 13.29 13.66 13.13 12.71 12.27 ~ 331 1
23 NGC 3353 AGN 10 45 22.390 +55 57 37.36 12.90 13.25 12.79     ~ 327 1
24 Mrk 36 SBG 11 04 58.298 +29 08 16.54   15.50 15.29     ~ 215 0
25 UGC 6456 bCG 11 28 00.43 +78 59 38.4   14.50       ~ 312 1
26 UGC 6538 GiC 11 33 17.08 +49 17 03.6   16.0       ~ 17 0
27 Mrk 178 bCG 11 33 29.12 +49 14 17.4 14.69 14.61 14.25 14.17   ~ 216 1
28 LEDA 39402 H2G 12 17 17.093 -28 02 32.67   17       ~ 127 0
29 Mrk 209 bCG 12 26 16.02 +48 29 36.6   15.3       ~ 310 0
30 UGCA 290 IG 12 37 21.7 +38 44 28   17       ~ 66 1
31 UGC 8091 H2G 12 58 40.1930291852 +14 13 00.737117016 15.24 15.16 14.98 14.81   ~ 443 0
32 NGC 5253 AGN 13 39 55.990 -31 38 24.11 11.48 10.94 10.49 10.33   ~ 1281 4
33 Mrk 829 GiP 14 50 56.495 +35 34 18.27   14.5 14.83     ~ 195 0
34 NAME UMi Galaxy G 15 09 11.34 +67 12 51.7   13.60 10.6     ~ 1207 0
35 IC 4662 bCG 17 47 09.192 -64 38 19.25   11.75 11.1 10.45   ~ 221 4
36 NAME Aquarius Dwarf G 20 46 51.7 -12 50 54 15.75 15.18 14.83 14.46   ~ 399 1
37 NGC 7468 bCG 23 02 59.172 +16 36 16.20   14.0       ~ 154 0
38 NGC 7625 IG 23 20 30.132 +17 13 32.16 13.31 13.23 11.98 11.25   ~ 245 0
39 Mrk 324 G 23 26 32.783 +18 16 00.07   15.5       ~ 63 0
40 [GRZ88] Region A PoG ~ ~           ~ 3 1
41 [GRZ88] Region C PoG ~ ~           ~ 3 0
42 [GRZ88] Region B PoG ~ ~           ~ 3 1
43 NAME Local Group GrG ~ ~           ~ 7181 0

    Equat.    Gal    SGal    Ecl

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2021.03.02-02:54:13

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