2008A&A...482..215M


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.09CEST07:33:16

2008A&A...482..215M - Astronomy and Astrophysics, volume 482, 215-227 (2008/4-4)

M1-78: a nitrogen-rich Galactic compact HII region beyond the Perseus arm.

MARTIN-HERNANDEZ N.L., ESTEBAN C., MESA-DELGADO A., BIK A. and PUGA E.

Abstract (from CDS):

There is considerable controversy surrounding the nature of M1-78, a compact nebula located beyond the Perseus arm. It was first classified as a planetary nebula and is nowadays generally considered to be a compact HII region. To investigate the nature of M1-78 further, we present a detailed spectroscopic study of M1-78 in the optical and near-infrared. We obtained long-slit, intermediate-resolution, optical spectroscopy with the ISIS spectrograph mounted on the William Herschel Telescope (WHT) at Roque de los Muchachos Observatory (La Palma, Spain). As a complement, we obtained long-slit, intermediate-resolution, near-infrared spectra using LIRIS, the near-infrared imager/spectrographer also installed at the WHT. M1-78 is a high-density nebula with substantial physical differences between its two main morphological zones: a bright arc in the SW and a blob of emission in the NE. Specifically, the blob in the NE has a higher electron temperature (13400K) and visual extinction (about 9mag) than the SW arc. The most important result, however, is the confirmation of a nitrogen enrichment in M1-78. This enrichment is stronger at the location of the NE blob and is correlated with a defficiency in the O abundance and a (dubious) He enrichment. Such an abundance pattern is typical of ejecta nebulae around evolved massive stars such as Wolf-Rayet and Luminous Blue Variable stars. The spatial variations in the physical conditions and chemical abundances and the presence of more than one possible ionizing source indicate, however, that M1-78 is better described as a combination of a compact HII region + ejecta. This is confirmed by the HeI2.112µm/Brγ line ratio, which indicates a hot (Teff>40000K) O star in the SW arc. Finally, we detect H2 emission that extends over a large (∼30") area around the ionized nebula. Analysis of the near-infrared H2 lines indicates that the excitation mechanism is UV fluorescence.

Abstract Copyright:

Journal keyword(s): infrared: ISM - ISM: individual objects: M1-78 - ISM: HII regions - ISM: abundances - stars: early-type - stars: Wolf-Rayet

Simbad objects: 15

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Number of rows : 15

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 LIN 495 Em* 01 12 19.7043742663 -73 51 26.025575647 14.62 14.61 14.63   14.49 (kA5mF0)/B[e] 19 0
2 NAME Per Arm PoG 03 30 +45.0           ~ 1304 0
3 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15340 1
4 M 42 HII 05 35 17.3 -05 23 28           ~ 3794 0
5 HD 50896 WR* 06 54 13.0440847499 -23 55 42.020318514 5.74 6.63 6.91 7.74   WN4b 749 0
6 NGC 2359 HII 07 18 30.000 -13 13 36.00           ~ 161 0
7 NGC 3576 HII 11 11 49.8 -61 18 14           ~ 229 2
8 BD+33 2642 pA* 15 51 59.8857490337 +32 56 54.327647794 9.806 10.61 10.73 10.884 10.961 O7p 388 0
9 SNR G002.4+01.4 HII 17 45 50.0 -26 14 28           ~ 55 2
10 * P Cyg s*b 20 17 47.2020844 +38 01 58.552724 4.66 5.24 4.82 4.28 4.02 B1-2Ia-0ep 1141 1
11 IRAS 21190+5140 HII 21 20 44.8 +51 53 28           ~ 128 2
12 HD 205314 ** 21 32 56.5913653851 +49 58 39.470136422   5.721 5.755     A0V 65 0
13 BD+28 4211 HS* 21 51 11.0220905905 +28 51 50.366090892 8.922 10.25 10.58 10.656 10.831 sdO2VIIIHe5 749 0
14 BD+25 4655 HS* 21 59 41.9751489837 +26 25 57.398356446 8.27 9.39 9.68     sdO6 104 0
15 NAME Local Arm reg ~ ~           ~ 397 0

    Equat.    Gal    SGal    Ecl

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