Revisiting Rubin’s Galaxy; fuel supply

 I already talked about Rubin’s Galaxy, the largest disk galaxy in the Local Universe before. It remains a really fun galaxy to study in detail with other instruments. And that is what my collaborators on this (longstanding) project recently did:

A multiwavelength overview of the giant spiral UGC 2885

Carvalho+

arXiv:2410.16467

The first figure, just to establish that indeed Rubin’s Galaxy is a frikkin giant.

This was a good paper to collate all the stats on this galaxy in one spot. This will make it easier to refer to when we will study the gas supply and star-formation rate of this galaxy in the rest of the paper. The underlying idea is that it may point to how low surface brightness galaxies are perhaps a different mode of star-formation in galaxies. 

First new observations: SITELLE. This is a unique instrument in that it is an IFU but works interferometrically. Short bandwidth (wavelength range) but the longer you observe, the higher your spectral resolution becomes. Wild! 

The SITELLE mapping of Rubin’s Galaxy in three narrow wavelength ranges. 

Second instrument is CO measurements using IRAM. This is to establish the molecular hydrogen reservoir. We already have HI observations of this galaxy. 

The IRAM map of Rubin’s galaxy.

The IRAM observations also give a rotation map. 

Blue and red map but not about elections. Galaxy rotation observed!

HI and IRAM observations combined: all the gas fit to form stars.

The SITELLE observations gave us a — spatially resolved — map of the metallicity of Rubin’s Galaxy. It is mostly metal-poor. 

So between the gas map and the current star-formation rate across the disk. The SFR was measured from the WISE fluxes. 

So at the present consumption rate, how long will it be before Rubin’s Galaxy runs out of fuel?

The stellar mass and star-formation rate of galaxies and Rubin’s Galaxy, color-coded by depletion time of the H2 (molecular gas) supply inferred from IRAM observations. Over 10 billion years!

The stellar mass and star-formation rate of galaxies and Rubin’s Galaxy, color-coded by depletion time of the H2 (molecular gas) supply inferred from HI observations. Over 10 billion years!

Rubin’s galaxy has over 10 Billion years of fuel left in the tank! Well over a Hubble time, the current age of the Universe!!