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.
I have a few questions about it, if I may:
a) at the top of p5, “Here we define a bulge dominated spiral as a galaxy visually selected as a spiral by Galaxy Zoo, but having a light proﬁle best ﬁt by a de Vaucouleur proﬁle (i.e. fracdeV > 0.5 from the SDSS pipeline).” – in what band? In my experience, lots of galaxies have fracdeV 0.8 in i (or z). Oh, and there’s an ‘s’ missing!
b) concerning the limitations due to spectra fibers covering only the centers of sample galaxies: has any thought been given to finding the spectra of ‘non-central’ objects (with unique SDSS ObjIds), if any? These may be bright clumps in a spiral arm, or a bar, for example.
c) where do M31 (the biggest spiral in the Local Group), M33 (smallest), and M32 (or M110, the only non-dwarf ellipticals) fit in Figure 6 (i.e. what are their masses)?
d) On p4: “We show the normalised colour distributions
(k-corrected to z = 0)” – what k-correction code was used?