Halpha3: Halpha imaging survey of HI selected galaxies from ALFALFA

TL;DR

Halpha3 is an imaging survey of approximately 400 HI-rich galaxies in the local universe, aiming to study the relationship between atomic gas and star formation across different environments and galaxy types.

Contribution

This survey provides the first comprehensive Halpha imaging data for a large, HI-selected galaxy sample in the local universe, linking gas content to star formation.

Findings

Good agreement between Halpha fluxes from imaging and SDSS spectra

Derived star formation rates for the galaxy sample

Established relationships between gas content and star formation across environments

Abstract

We present Halpha3 (acronym for Halpha-alpha-alpha), an Halpha narrow-band imaging survey of ~400 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster. By using hydrogen recombination lines as a tracer of recent star formation, we aim to investigate the relationships between atomic neutral gas and newly formed stars in different environments (cluster and field), morphological types (spirals and dwarfs), and over a wide range of stellar masses (~10^7.5-10^11.5 Msun). We image in Halpha+[NII] all the galaxies that contain more than 10^7 Msun of neutral atomic hydrogen in the sky region 11^h < R.A. <16^h 4^o < Dec. <16^o; 350< cz <2000 km/s using the San Pedro Martir 2m telescope. This survey provides a complete census of the star formation in HI rich galaxies of the local universe. We present the properties of the galaxy sample, together with Halpha fluxes and equivalent widths. We find an excellent agreement between the fluxes determined from our images in apertures of 3 arcsec diameter and the fluxes derived from the SDSS spectral database. From the Halpha fluxes corrected for galactic and internal extinction and for [NII] contamination we derive the global star formation rates (SFRs).