Thursday, May 23, 2013

Daily Paper #9: WISE TF: A Mid-infrared, 3.4-micron Extension of the Tully-Fisher Relation Using WISE Photometry

Here's the recent WISE paper my supervisor had sent me a link to.
Title:WISE TF: A Mid-infrared, 3.4-micron Extension of the Tully-Fisher Relation Using WISE Photometry
Authors: Lagattuta, Mould et al.
Year: 2013,
In a way, this is a classic, straightforward observational TFR paper. They pick the shortest wavelength (3.4 um) WISE band, where dust emission is not very important, use archival HI linewidths from Hyperleda and Cornell HI archive and WISE photometry (w1gmag magnitudes). They also take morphological classifications from CfA ZCAT and axis ratios from V-band measurements in NED. They reject galaxies with low quality of radio observations and inclinations (from b/a) less than 45 deg, as well as all E galaxies.
What was interesting for me here was that they did a number of corrections in a thorough way, especially the peculiar velocities correction. Since their and CALIFA redshifts overlap, we might have to give more thought to this correction, as it can reduce scatter in the resulting TFR significantly. They use the Erdoglu 2006 model, interpolating over the velocity grid where necessary (I'll read it for tomorrow).
The intrinsic extinction correction are small in the mid IR, but not so in the SDSS r-band. I'll check Masters 2003 correction prescription too, maybe it's better than the one I'm using.
They also find a bend in their TFR, due to different morphological types -- like we do (the slopes for late and early spirals are different), which is worth mentioning! However, they normalise the magnitudes of the early types and force them to fit the late-type spirals relation. Since our sample is dominated by early-type spirals, I would not want to do that (and I'm not sure what physical basis there is for this correction).
There is a reference to a 2013 paper by Sorce et al., where it is claimed that redder galaxies lie above the TF relation, and the bluer ones lie below, that's interesting.
They also discuss the influence of a bulge to the scatter of TFR, which is larger at the IR and for massive galaxies -- I'll remember that.
What made me think is their conclusion that the mid-IR W1 and 2MASS K bands trace the same stellar populations, a significant fraction of which are in the central parts of the galaxies (thus, probably bulges, esp. in CALIFA sample). That is interesting, in part because we make the inclination and extinction corrections assuming the galaxies are thin disks. Also, we have to keep in mind that when we plot the TFR for different bands, we are relating disk rotation velocities with different morphological components of a galaxy, which do not necessarily correspond to the disk only!

No comments:

Post a Comment