Paper day ( https://arxiv.org/abs/2011.04990 ): Lead by me and @KatjaFah, incl. @lellifede, @8minutesold, @styrofoamplates and more. We aquired 20 hours of MUSE time to follow-up dwarf galaxies around Cen A.

Dwarf galaxies are faint, and therefore hard to observe. However, the IFU capability of MUSE enables us to integrate the spectrum over the whole galaxy, making such observations possible.

The signal to noise ranges from fantastic to whelp (but fittable with ppxf):

We got velocities for all, and metallicities and ages for some of the 12 dwarfs we observed. Here we see the metallcity-luminosity relation of the Local Group. The red dots (our observations) follow nicely this scaling relation.

We also found some Globular Clusters (GCs). In total, three of the dwarfs hosted stellar clusters. For those we could of course extract spectra as well (that's IFU for you).

Here's the specific frequency of the GCs for different galaxies, our dwarfs nicely follow the relation spanned by the Local Group dwarfs and other nearby and not so nearby galaxies.

But we can not only find GCs, but even individual stars in the dwarfs. Okay, ONE individual star, which is a planetary nebula (PN). But still. that is fricking cool. Here is the spectrum of one such PNe candidate. The OIII and Halpha are really indicative.

This PN is found around KK197 (red cross). Because we have several stellar clusters (the circles) we could do a dynamical analysis. The PN is 50km/s apart from the mean of the group, is is probably an interloper from the outer halo of Cen A.

Similar to what @DokkumPieter, @DanieliShany, @nfmartin1980, @Nico_Longeard and others did for UDGs, we calculated the velocity dispersion within one effective radius from the GCs.

And put the estimated accelaration on the Radial Acceleration Relation (RAR, by @DudeDarkmatter, @lellifede). Within the errors, it is consistent with the dwarfs of the Local Group. However, it is also quite consistent with DF2&DF4. I am not saying it is lacking dark matter...

... just that the uncertainties are too large to be conclusive. Don't you go out and say we discovered a dark matter free dwarf galaxy, folks. ;-)

We also made predictions in MOND for the velocity dispersion, including the (in)famous external field effect (EFE, cc @DataAnatomist). Well, looks like it fits within the uncertainties. But again, the uncertainties are too large to be decisive.

What we discovered (and with we I mean @KatjaFah) – which is mind-boggling – is this Halpha ring. It is somehow offset from the center of KK203 and has a diameter of 440 pc. That's one large structure for you...

Where does it come from? Post-AGB stars ionizing the gas? Nope (see paper). AGN feedback? Nope (see paper). Shocking through a passage by Cen A? Nope (see paper). Is it a Super Nova Renmant? Perhaps (you guessed it, see paper).

Originally, we just wanted to get the velocities of the dwarfs to study the motion with respect to the putative pancake-of-satellites around Cen A, but there were soo many other exciting things, that it quickly outgrew one paper, which is why we split it.

So in the near future we will put another paper on the dynamics of the Cen A system online. I got the last round of comments from my collaborators, but then Covid-19 hit me and I am not up for the game yet. Please be patient with me.

To summarize, we got MUSE data for 12 dwarf galaxies around Cen A and got some really exciting science out of it, exploiting the fantastic capabilitites of IFU technology. Check out the paper ( https://arxiv.org/abs/2011.04990 ) if you love dwarfs as much as I do – I dare you.