# New ALMA constraints on the star-forming ISM at low metallicity: A 50 pc view of the blue compact dwarf galaxy SBS0335-052

## TL;DR

This study uses high-resolution ALMA observations to investigate the cold interstellar medium in the low-metallicity galaxy SBS0335-052, revealing a large cold gas reservoir and setting constraints on molecular gas properties.

## Contribution

First high-resolution ALMA observations of a low-metallicity galaxy's cold ISM, providing new constraints on molecular gas and dust properties at 52 pc scale.

## Key findings

- CO J=2-1 line not detected, setting upper limits on molecular gas.
- Detected continuum suggests a significant cold dust component.
- Evidence for a large cold gas reservoir unseen in CO.

## Abstract

Properties of the cold interstellar medium of low-metallicity galaxies are not well-known due to the faintness and extremely small scale on which emission is expected. We present deep ALMA band 6 (230GHz) observations of the nearby, low-metallicity (12 + log(O/H) = 7.25) blue compact dwarf galaxy SBS0335-052 at an unprecedented resolution of 0.2 arcsec (52 pc). The 12CO J=2-1 line is not detected and we report a 3-sigma upper limit of LCO(2-1) = 3.6x10^4 K km/s pc^2. Assuming that molecular gas is converted into stars with a given depletion time, ranging from 0.02 to 2 Gyr, we find lower limits on the CO-to-H2 conversion factor alpha_CO in the range 10^2-10^4 Msun pc^-2 (K km/s)^-1. The continuum emission is detected and resolved over the two main super star clusters. Re-analysis of the IR-radio spectral energy distribution suggests that the mm-fluxes are not only free-free emission but are most likely also associated with a cold dust component coincident with the position of the brightest cluster. With standard dust properties, we estimate its mass to be as large as 10^5 Msun. Both line and continuum results suggest the presence of a large cold gas reservoir unseen in CO even with ALMA.