Pox 186: an ultracompact galaxy with dominant ionized gas emission

Abstract

We present a ground-based optical spectroscopic and HST U, V, I photometric study of the blue compact dwarf (BCD) galaxy Pox 186. It is found that the emission of the low-surface brightness (LSB) component in Pox 186 at radii < 3'' (< 270 pc in linear scale) is mainly gaseous in origin. We detect Halpha emission out to radii as large as 6''. At radii > 3'' the light of the LSB component is contaminated by the emission of background galaxies complicating the study of the outermost regions. The surface brightness distribution in the LSB component can be approximated by an exponential law with a scale length alpha < 120 pc. This places Pox 186 among the most compact dwarf galaxies known. The derived alpha is likely to be an upper limit to the scale length of the LSB component because of the strong contribution of the gaseous emission. The oxygen abundance in the bright HII region derived from the 4.5m Multiple Mirror Telescope (MMT) and 3.6m ESO telescope spectra are 12+log(O/H)= 7.76+/-0.02 and 7.74+/-0.01 (~ Zsun/15), respectively, in accordance with previous determinations. The helium mass fractions found in this region are Y=0.248+/-0.009 (MMT) and Y=0.248+/-0.004 (3.6m) suggesting a high primordial helium abundance.

arXiv comment11 pages, 9 Postscript figures

References in corpus (17)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Heavy element abundances in blue compact galaxies
• Palomar/Las Campanas Imaging Atlas of Blue Compact Dwarf galaxies: I. Images and integrated photometry
• Systematic effects and a new determination of the primordial abundance of 4He and dY/dZ from observations of blue compact galaxies
• Helium abundance in the most metal-deficient blue compact galaxies: I Zw 18 and SBS 0335-052
• SBS 0335-052, a probable nearby young dwarf galaxy: evidence pro and con
• Line temperatures and elemental abundances in HII galaxies
• The blue compact dwarf galaxy I Zw 18: a comparative study of its low-surface-brightness component
• New insights to the photometric structure of Blue Compact Dwarf Galaxies from deep Near-Infrared studies I. Observations, surface photometry and decomposition of surface brightness profiles
• The First Deep ACS Lyman alpha Images of Local Starburst Galaxies
• Modeling the emission line sequence of H II galaxies
• Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies. III. SBS 1415+437
• An imaging and spectroscopic study of the very metal-deficient blue compact dwarf galaxy Tol 1214--277
• The evolutionary status of the low-metallicity blue compact dwarf galaxy SBS 0940+544
• The He abundance in the metal-deficient blue compact dwarf galaxies Tol 1214-277 and Tol 65
• Discovery of the high--ionization emission line [Ne V] 3426 in the blue compact dwarf galaxy Tol 1214-277
• POX 186: A Dwarf Galaxy in the Process of Formation?

Cited by in corpus (23)

• Galaxy Zoo Green Peas: Discovery of A Class of Compact Extremely Star-Forming Galaxies
• The Mass-Metallicity Relation with the Direct Method on Stacked Spectra of SDSS Galaxies
• Low-redshift Lyman continuum leaking galaxies with high [OIII]/[OII] ratios
• MMT/MMIRS spectroscopy of $z=1.3-2.4$ extreme [OIII] emitters: Implications for galaxies in the reionization-era
• "Counterpart" method for abundance determinations in HII regions
• Extremely metal-poor star-forming galaxies. New detections and general morphological and photometric properties
• The size--density relation of extragalactic HII regions
• Balmer jump temperature determination in a large sample of low-metallicity H II regions
• New Methods for Identifying Lyman Continuum Leakers and Reionization-Epoch Analogues
• I Zw 18 as morphological paradigm for rapidly assembling high-z galaxies
• Dust emission in star-forming dwarf galaxies: General properties and the nature of the sub-mm excess
• The Semi-forbidden CIII]$\lambda$1909Å~ Emission in the Rest-Ultraviolet Spectra of Green Pea Galaxies
• New southern blue compact dwarf galaxies in the 2dF Galaxy Redshift Survey
• A multiwavelength study of the Magellanic-type galaxy NGC 4449 - I. Modelling the spectral energy distribution, the ionization structure and the star formation history
• On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies: GMOS-IFU spectroscopy and SDSS photometry of the double-knot galaxy HS 2236+1344
• The Red Halo Phenomenon
• The Globular Cluster System of NGC 1399 IV. Some noteworthy objects
• A search for HI in some peculiar faint dwarf galaxies
• Bulgeless disks, dark galaxies, inverted color gradients, and other expected phenomena at higher z. The chromatic surface brightness modulation (CMOD) effect
• One of Everything: The Breakthrough Listen Exotica Catalog
• MUSE observations of the blue compact dwarf galaxy Haro 14. Data analysis and first results on morphology and stellar populations
• Evolutionary synthesis models as a tool and guide towards the first galaxies
• Unveiling an old disk around a massive young leaking blueberry in SDSS-IV MaNGA