From: Serena Nobili (serena@physto.se)
Date: Tue Feb 25 2003 - 04:47:16 PST
Hi Rob
I hope I am not too late for my comments on the HST paper.
I have checked the comments by the others and I hope I did not miss
anything. My most relevant comments are about intrinsic dispersion of
course ;)
1) Table 3 and Table 5
As Isobel said there is some confusion in the captions of table 3.
Moreover you say (in note 5-table3 and note 4-table 5) that you assume a
0.03 intrinsic dispersion for rest frame B-V at Bmax. This is not consistent
with our paper (Nobili et al.) where we give an estimate of 0.07 at Bmax.
2) Pag.13
About the ridge-line fit, you should say why you decided not to
apply the host galaxy extinction corrections, as computed by Phillips for
instance, and why you think the ridge-line fit is more appropriate for
this (I guess you don't want to be dependent on Phillips estimates). This
depends also on how you decide the size of the asymmetry needed to account
for the host extinction (see Saul comments). On the other hand as Isobel
pointed out, maybe this all should go in an appendix instead.
This could be relevant to the discussion about the U-B, later in the
section, when you say you use the Phillips extinctions to correct them,
since there are not enough data to do the ridge-line fit.
3) Greg wrote:
> Intrinsic color uncertainty:
>
> This really hits us hard, especially in U-B. I am not yet convinced that
> intrinsic color dispersion has been proven, at least not for B-V. For
> instance, can it be demonstrated that variations in the dust extinction
> law are not to blame?
> This is a big difference for the errors, since an intrinsic color error
> is multiplied by R_B while an error in R_B is multiplied by E(B-V), the
> latter being
> much smaller. I looked at the Nobili et al paper, and also Jha's thesis,
> and have my reservations about putting this error in at its current
> size.
As written in the Nobili et al. (end of the section "Discussion"), I
have tried to introduce an uncertainty on the dust extinction law, e.g. I
considered an Rv=3.1 +- 1.0. Propagating this in the uncertainty of the
host galaxy extinction corrections does not change the computed intrinsic
dispersion given in the paper by significant amounts.
4) on a completely different issue, at the end of pag. 6 you say:
"Fits were performed to template lightcurves, and were performed
simultaneously to the R and I band data..."
I am always very confused about the meaning of "simultaneously" when
speaking about fitting curves to data. Does it mean you impose the same
stretch for both of them or some other parameters, or what else?
I send a copy to the deepnews list also since many commented on the
intrinsic colours issue.
Cheers,
- Serena
----------------------------------------------------------------------
www.physto.se/~serena
Tel +46 8 55378661
Give free food at:
http://www.porloschicos.com/
http://www.thehungersite.com/
This archive was generated by hypermail 2.1.4 : Tue Feb 25 2003 - 04:47:34 PST