High-Ionization Emission in Metal-deficient Blue Compact Dwarf Galaxies

By T. Thuan, Y. Izotov. 2005

164 citations recorded by the source corpus.

Primordial stars are expected to be very massive and hot, producing copious amounts of hard ionizing radiation. The best place to study hard ionizing radiation in the local universe is in very metal-deficient blue compact dwarf (BCD) galaxies. We have carried out a MMT spectroscopic search for [Ne V] λ3426 (ionization potential of 7.1 ryd), [Fe V] λ4227 (ionization potential of 4 ryd), and He II λ4686 (ionization potential of 4 ryd) emission in a sample of 18 BCDs. We have added data from previous work and from the Data Release 3 of the Sloan Digital Sky Survey. In total, we have assembled a BCD high-ionization sample with [Ne V] emission in four galaxies, [Fe V] emission in 15 galaxies, and He II emission in 465 galaxies. With this large sample, we have reached the following conclusions. There is a general trend of higher [Ne V], [Fe V], and He II emission at lower metallicities. However, metallicity is not the only factor that controls the hardness of the radiation. High-mass X-ray binaries and main-sequence stars are probably excluded as the main sources of the very hard ionizing radiation responsible for [Ne V] emission. The most likely source of [Ne V] emission is probably fast radiative shocks moving with velocities ≳450 km s-1 through a dense interstellar medium with an electron number density of several hundreds cm-3 and associated with supernova explosions of the most massive stars. These have masses of ~50-100 M☉ and are formed in very compact super-star clusters (SSCs). The softer ionizing radiation required for He II emission is likely associated with less massive evolved stars and/or radiative shocks moving through a less dense interstellar medium.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b66125ffd420221381d7e750ab10daef9a6f94fb

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

Star formation sustained by gas accretion (2014, background): “proto-galactic cloud (Kunth and Lebouteiller 2011), the metallicity threshold set by the ejecta from population III stars (Audouze and Silk 1995; Thuan and Izotov 2005),”
THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE “GREEN PEA” GALAXIES (2013, background): “The presence of weak [Fev] λ4227 emission and high-velocity emission-line wings in II Zw 40 supports the Ionizing Radiation in the Green Peas 23 24 Jaskot & Oey shock hypothesis (Thuan & Izotov 2005).”
Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: physical properties and implications for studies at z > 7 (2014, background): “These systems also show prominent emission from CIVλ1549, requiring a substantial flux of photons with energies greater than 47.9 eV, similar to the local population of blue compact dwarfs (e.g., Thuan & Izotov 2005).”
VERY STRONG EMISSION-LINE GALAXIES IN THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY AND IMPLICATIONS FOR HIGH-REDSHIFT GALAXIES, (2011, methodology): “This object is comparable to the most metal-deficient galaxies found in the USEL sample (Hu et al. 2009) and close to the lowest metallicity star-forming galaxies known, IZw 18 (Thuan & Izotov 2005) and SBS033552 (Izotov et al. 2006).”
The Primordial Abundance of 4He: A Self-consistent Empirical Analysis of Systematic Effects in a Large Sample of Low-Metallicity H II Regions (2007, background): “The details of data reduction are described in Thuan & Izotov (2005) and are the same as those for other H ii regions from the HeBCD sample.”
Strongly star forming galaxies in the local Universe with nebular He iiλ4686 emission (2012, methodology): “The excellent analysis of Thuan & Izotov (2005) is another example, where the focus was on BCD galaxies.”