Blueberry galaxies up to 200 Mpc and their optical and infrared properties^⋆

¹ Astronomical Institute, Academy of Sciences, Boční II 1401, 14131 Prague, Czech Republic
e-mail: konstantinos.kouroumpatzakis@asu.cas.cz
² Department of Physics, University of Crete, Voutes University campus, 70013 Heraklion, Greece
³ Institute of Astrophysics, Foundation for Research and Technology-Hellas, N. Plastira 100, Vassilika Vouton, 71110 Heraklion, Greece
⁴ Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
⁵ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
⁶ Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlářská 2, Brno 61137, Czech Republic

Received: 27 February 2024
Accepted: 2 May 2024

Abstract

Context. Dwarf highly star-forming galaxies (SFGs) dominated the early Universe and are considered the main driver of its reionization. However, direct observations of these distant galaxies are mainly confined to rest-frame ultraviolet and visible light, limiting our understanding of their complete properties. Therefore, it is still paramount to study their local analogs, the green pea (GP) and blueberry (BB) galaxies.

Aims. This work aims to expand our knowledge of BBs by identifying a new sample that is closer and in the southern sky.

Methods. In addition to the already known BBs, this new sample will allow for a statistically significant study of their properties probed by visible and infrared (IR) light. By utilizing the HECATE catalog, which provides optical and IR photometry and characterization of galaxies, along with data from Pan-STARSS and SDSS, this study selects and analyzes a new sample of BBs. We employed spectral energy distribution fitting to derive homogeneous measurements of star-formation rates and stellar masses. Additionally, we measured emission-line fluxes, including He II λ4686, through spectral fitting.

Results. Through this work, we identified 48 BBs, of which 40 were first recognized as such, with the nearest at 19 Mpc. Fourteen of the BBs are in the south sky. The BBs tend to be extremely IR red in both WISE W1 – W2 and W2 – W3 colors, distinguishing them from typical SFGs. Dwarf SFGs with higher specific star-formation rates tend to have redder IR colors.

Conclusions. Blueberry galaxies stand out as the most intensely star-forming sources in the local Universe among dwarf galaxies. They are intrinsically bluer in visible light, redder in the infrared, and less massive. They also have higher specific star-formation rates, equivalent widths, lower metallicities, and the most strongly ionized interstellar medium compared to typical SFGs and GPs.