An EVLA search for water megamaser emission in the submm galaxy SMM J16359+6612 at z=2.5

TL;DR

This study used the EVLA to search for water megamaser emission in a high-redshift submm galaxy, setting upper limits on megamaser luminosity and discussing implications for galaxy evolution and redshift determination methods.

Contribution

First search for H2O megamasers in a z=2.5 submm galaxy, providing constraints on megamaser luminosity and implications for galaxy evolution studies.

Findings

No H2O megamaser emission detected.

Luminosity upper limit set at 5305 solar luminosities.

Blind searches may not effectively determine redshifts for less luminous submm galaxies.

Abstract

Using the Expanded Very Large Array, we have conducted a search for 22.2 GHz H2O megamaser emission in the strongly lensed submm galaxy, SMM J16359+6612 at z=2.517. This object is lensed into three components, and after a correction for magnification is applied to its submm-wavelength flux density, it is typical of the bulk of the high-redshift, submm galaxy population responsible for the 850 um extragalactic background (S(850um)~1 mJy). We do not detect any H2O megamaser emission, but the lensing allows us to place an interesting constraint on the luminosity of any megamasers present, L(H2O) < 5305 solar luminosities for an assumed linewidth of 80 km/s. Because the far-infrared luminosity in submm galaxies is mainly powered by star formation, and very luminous H2O megamasers are more commonly associated with quasar activity, it could be that blind searches for H2O megamasers will not be an effective means of determining redshifts for less luminous members of the submm galaxy population.