Extended emission and star formation in I Zw 18

Journal Article · Thu Feb 01 04:00:00 EST 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168369· OSTI ID:6966171

Dufour, R J; Hester, J J ^[1]

---

1. Rice Univ., Houston, TX (USA) California Institute of Technology, Pasadena (USA)

The results of sky limited emission-line (H-alpha and forbidden O III 5007A) and line-free (6450 A and 5100 A) continuum imagery of the super-metal-poor blue compact galaxy I Zw 18 are reported. The main body of star formation in the galaxy is surrounded by a 3 kpc diameter extended envelope in H-alpha. In addition, there exist arcs of emission emanating from both central H II regions and winding around to the west, as well as a broader ridge of emission extending northward from the main body. The total mass of ionized material is estimated to be 3 x 10 to the 6th solar masses, or about 5 percent of the mass of the observed H I clouds. Several extended stellar continuum regions exist to the northwest of the main body, the brightest three forming a line along PA = 310 deg out to a 3 kpc distance from the central region of the galaxy. The correlation of the morphology and location of stellar continuum and emission regions with the distribution of H I is discussed. It is calculated that I Zw 18 has had previous, but disconnected, episodes of star formation, possibly from chance collisions of widely separated H I clouds. 17 refs.

• OSTI ID: 6966171
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 350; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BALMER LINES
COLLISIONS
COLOR
COSMIC RADIO SOURCES
EMISSION SPECTRA
GALACTIC EVOLUTION
GALAXIES
H1 REGIONS
H2 REGIONS
INTERSTELLAR SPACE
MASS
MORPHOLOGY
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
SPACE
SPECTRA
STAR EVOLUTION