Last wk "Apertif view of OH Megamaser IRAS10597+5926: OH 18 cm satellite lines in wide-area HI surveys" was accptd: we serendipitsly detectd an OHmegamaser in our HI survey! w @Avendedoraldera @astrohayley @betseeeey Thought I'd go into a lil more detail.. http://arxiver.moonhats.com/2021/01/18/apertif-view-of-the-oh-megamaser-iras-105975926-oh-18-cm-satellite-lines-in-wide-area-hi-surveys-ga/

So, first, what are they? Astronomical masers are naturally occurring phenomena of stimulated emission. They work, in principle, the same way lasers work, but at microwave wavelengths instead of at visible light wavelengths (laser --> maser). https://en.wikipedia.org/wiki/Astrophysical_maser 2/

Masers are found in star forming regions in the Milky Way, or the centers of other galaxies, coming from gas very close to the central blackhole. Extragalactic masers are a million times brighter than those we see in the MW, so they are known as <Dr.Evil voice> *MEGA* masers. 3/

But, OH (hydroxl) megamasers aren't found in every galaxy nucleus, they need special conditions. For example, they are highly correlated w galaxies that also have intense star formation, dense gas, and galaxy mergers (and as a result are also very bright in infrared emission). 4/

We can do some cool cosmology, modeling, & fundamental physics w OH megamasers (OHMs). Cosmo: if we survey a large volume of space to large distances, can use the frequency of OHMs to trace the galaxy merger history of the Universe &test our understanding of galaxy evolution. 5/

Maser modeling: OH has four spectral lines around 18 cm, and the relative strengths of the lines (at 1612, 1665, 1667, and 1720 MHz) can tell us what the physical conditions are like in the OH emitting clouds, even if we can't resolve the emitting structures themselves. 6/

Physics: the relative frequencies of OH lines have diff dependencies on the fine structure constant. By detecting multiple lines at high redshift (farther away, further back in time), we can test whether "alpha" is constant over history of the Universe. 7/ https://en.wikipedia.org/wiki/Fine-structure_constant

Thing is OHMs are rare (<150 known) &hard to find (always in IR bright galaxies, but not all IR bright galaxies have OHMs). But wide-area radio surveys like Apertif, designed to detect 21 cm atomic hydrogen, can detect OH when its redshifted to z>0.166. 8/ https://www.astron.nl/telescopes/wsrt-apertif/

So, that's what happnd! Apertif found its 1st OHM (images from paper) & (1) it's *really* bright--almost a gigamaser (2) forming stars like crazy--more than 100 M_Sun/yr (3) prob a late stage galaxy merger & (4)we can constrain the 1667/1612 line ratio better than ever before. 9/

The dominant emission in IRAS 10597+5926 is in 1667 MHz line (orange) & to a lesser degree in 1665 MHz line (green)--typical for OHMs. The red line shows predicted location of the 1612 MHz line, observed simultaneously thanks to the Apertif's large bandwidth. 10/

We can compare the line ratios w maser pumping models... 1667/1665 ratios have a broad range typically ~5 (ours is 5.5), and our limiting 1667/1612 ratio is 45.9, the highest reported yet. (I'll let you read the paper for commentary on this tho--it gets a bit more technical.) 11/

We also predict Apertif will eventually detect 100-150 OHMs including a few in the faintest spectral lines (1612 & 1720 MHz), more than doubling the known OHM sample. Also good news for OHM searches, cosmology & fundamental physics w @SKA_Africa, ASKAP, @SKA_telescope 11/FIN