2000ApJ...538L..77V

Query : 2000ApJ...538L..77V

2000ApJ...538L..77V - Astrophys. J., 538, L77-L80 (2000/July-3)

No diffuse H₂ in the metal-deficient galaxy I Zw 18.

VIDAL-MADJAR A., KUNTH D., LECAVELIER DES ETANGS A., LEQUEUX J., ANDRE M., BENJAFFEL L., FERLET R., HEBRARD G., HOWK J.C., KRUK J.W., LEMOINE M., MOOS H.W., ROTH K.C., SONNEBORN G. and YORK D.G.

Abstract (from CDS):

The metal-deficient starburst galaxy I Zw 18 has been observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) in a search for H₂ molecules. The spectrum obtained with an aperture covering the full galaxy shows no absorption lines of diffuse H₂ at the radial velocity of the galaxy. The upper limit for the diffuse H₂ column density is found to be very low, N(H₂)≲10¹⁵ cm^–2 (10 σ), unlike our Galaxy where H₂ is generally present for even low H I column densities. Although the H I column density here is as high as N(H I) ~ 2x10²¹ cm^–2, we observe 2N(H₂)/N(H I) ≲ 10^–6. We cannot exclude the possibility that some H₂ could be in very dense, small, and discrete clumps that cannot be detected with the present observation. However, the remarkable absence of diffuse H₂ in this metal-poor galaxy can be explained by the low abundance of dust grains (needed to form this molecule from H atoms), the high ultraviolet flux, and the low density of the H I cloud surrounding the star-forming regions. Thus, having eliminated diffuse H₂ as a significant contributor to the total mass, it appears that the gas of the galaxy is dominated by H I and that the high dynamical mass is not composed of cold and diffuse baryonic dark matter.

Abstract Copyright: ∼

Journal keyword(s): Galaxies: Abundances - Galaxies: Dwarf - Galaxies: Individual: Alphanumeric: I Zw 18 - Galaxies: ISM - ISM: Molecules - Ultraviolet: Galaxies

Simbad objects: 1

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Number of rows : 1

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag U	Mag B	Mag V	Mag R	Mag I	Sp type	#ref 1850 - 2026	#notes
1	Mrk 116	AGN	09 34 02.1	+55 14 25						~	1179	1

Query : 2000ApJ...538L..77V

Basic data :

Mrk 116 -- Active Galaxy Nucleus
Other object types:	`PaG ()`, `G (Mrk,AGC,...)`, `AGN (2019MNRAS)`, `Opt (SDSS)`
ICRS coord. (ep=J2000) :	`09 34 02.1 +55 14 25 (Optical) [ ] D 2003A&A...412...45P`
FK4 coord. (ep=B1950 eq=1950) :	`09 30 30.3 +55 27 46 [ ]`
Gal coord. (ep=J2000) :	`160.5263 +44.8422 [ ]`
Radial velocity / Redshift / cz :	`V(km/s) 774 [~] / z(emission) 0.002585 [~] / cz 774.96 [~] (IR) C 2016ApJS..226...11S`
Morphological type:	`cG... D` `~`
Angular size (arcmin):	`2.0 2.0 90 (~) D` `2007ApJS..173..185G`

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`Mrk 116`	`KUG 0930+554`	`UGCA 166`	`[MI94] Im 58`
`AGC 190351`	`LEDA 27182`	`ZW I 18`
`CGPG 0930.5+5527`	`SBSG 0930+554`	`[HSN2016] J143.50+55.24`
`HS 0930+5527`	`SDSS J093401.92+551427.9`	`[M98c] 093030.3+552746`

References (1179 between 1850 and 2026) (Total 1179)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).

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Data at NED - NASA/IPAC Extragalactic Database : Mrk 116

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KUG 0930+554 SDSS J093401.92+551427.9

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