Tag Archive | Spectra

New paper on Red and Blue Spirals and Ellipticals

Just a quick note to point out a new paper based on Galaxy Zoo classifications appeared on the arxiv this morning (and just accepted to MNRAS): The Differing Star Formation Histories of Red and Blue Spirals and Ellipticals, by Rita Tojeiro et al. 

In this work we took samples of galaxies split by their morphological classifications (from you all, and actually going back to the original Galaxy Zoo project) as well as by their optical colour. With the help of an Ogden Trust undergraduate summer student (Joshua Richards) we then compiled the average star formation histories of these samples, based on fits of star formation models to the Sloan Digital Sky Survey spectra of the galaxies (previously published and called VESPA, or “VErsatile SPectral Analysis” by Rita).

Our main result was that red spirals differ in their star formation histories from blue spirals only in the last billion years or less. We also find that blue ellipticals have very similar star formation histories to blue spirals. We show some results about the dust and metal (astronomers metal) content of the galaxies as well. I think it’s a nice project and I’m very happy to see it finally finished and published.

Thanks again for the classifications.

Markarian and the Blob

Today’s OOTW features an OOTD written by Alice on the 15th of July.

117 million light years away there lies a Markarian galaxy and a very interesting companion. As Alice says in her OOTD, these Markarians are galaxies that emit strongly in ultraviolet and visible light, and are often a host to AGN.

During the observation run at Kitt Peak the Galaxy Zoo team had some spare telescope time going after observing a list of Voorwerpjes, so Bill Keel asked Zooites on the forum to provide objects to get a spectrum for:

MRK 490

MRK 490 and its blue companion.

The bright blue blobby companion just above the Markarian galaxy MRK 490 centred in the picture above was one such object that was observed. The companion is brimming with new stars as shown by the huge emission line (amongst others) of OIII at around 5000 angstroms in the spectrum below, the object is very close to the galaxy below it going by their redshift, so it is suspected to be interacting with it!

Spectrum for MKN 490's companion

Spectrum for MKN 490's companion; click for larger image.