On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies

Abstract

Aims. The main goal of this study is to carry out a spatially resolved investigation of the warm interstellar medium (ISM) in the extremely metal-poor blue compact dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on analysis of the spatial distribution of chemical abundances, emission-line ratios, and the kinematics of the ISM, and to the recent star-forming (SF) activity in this galaxy. Methods. This study is based on optical integral field unit spectroscopy data from Gemini Multi-Object Spectrograph (GMOS) at the Gemini North telescope and archival Sloan Digital Sky Survey (SDSS) images. The galaxy was observed at medium spectral resolution over the spectral range from ∼4300 Å to 7300 Å. The data were obtained in two different positions across the galaxy, obtaining a total 4 × 8 field that encompasses most of its ISM.Results. Emission-line maps and broad-band images obtained in this study indicate that HS 2236+1344 hosts three giant H ii regions (GH iiRs). Our data also reveal some faint curved features in the BCD periphery that might be due to tidal perturbations or expanding ionized-gas shells. The ISM velocity field shows systematic gradients along the major axis of the BCD, with its southeastern and northwestern half differing by ∼80 km s −1 in their recessional velocity over the field of view. The Hα and Hβ equivalent-width distribution in the central part of HS 2236+1344 is consistent with a very young (∼3 Myr) burst. Our surface photometry analysis reveals an underlying low surface brightness component with moderately red colors, which suggest that the galaxy has undergone previous star formation. We derive an integrated oxygen abundance of 12 + log(O/H) = 7.53 ± 0.06 and a nitrogen-to-oxygen ratio of log(N/O) = −1.57 ± 0.19. Our results are consistent, within the uncertainties, with a homogeneous distribution of oxygen and nitrogen within the ISM of the galaxy. The high-ionization He ii λ4686 emission line is detected only in the central part of HS 2236+1344. Similar to many BCDs with He ii λ4686 emission, HS 2236+1344 shows no Wolf-Rayet (WR) bump.

Arp 202: a TDG formed in a parent's extended dark matter halo?

“…This same phenomena has been also been observed in some other star-forming dwarf galaxies with single and multiple SF regions (e.g. Lagos et al 2009Lagos et al , 2012Lagos et al , 2014Lagos et al , 2016.…”

Exploring chemical homogeneity in dwarf galaxies: a VLT-MUSE study of JKB 18

“…(e.g. Skillman, Kennicutt & Hodge 1989;Kobulnicky & Skillman 1996;Lee, Skillman & Venn 2006;Kehrig et al 2008;Croxall et al 2009;James, Tsamis & Barlow 2010;Berg et al 2012;Lagos et al 2014Lagos et al , 2016Kumari et al 2019a) and small uncertainty (i.e. σ < 0.1).…”

Coevolution of metallicity and star formation in galaxies toz≃ 3.7 – I. A Fundamental Plane

“…For one galaxy in the starburst sample (UM 420), because of the lack of MIPS observations, the SFR was estimated from Hα luminosities, and for one galaxy (ESO 489−G56) there were no data available from which to infer SFR (so it was not considered further). For the (23) BCDs from Hunt et al (2010), total Hα fluxes were taken from Gil de Paz et al (2003); RosaGonzález et al (2007);Pérez-Montero et al (2011);Lagos et al (2014), and 24 µm fluxes from Hunt et al (2016, in prep.). As for the starbursts, for the three galaxies without Hα data, we used SFR(TIR); and for SBS 1030+583 there were no MIPS data so we adopted SFR(Hα).…”