From: Greg Aldering (aldering@panisse.lbl.gov)
Date: Mon Apr 05 2004 - 19:26:24 PDT
>From mobasher@stsci.edu Mon Apr 5 19:11:30 2004
>Date: Mon, 5 Apr 2004 22:11:28 -0400 (EDT)
>From: Bahram Mobasher <mobasher@stsci.edu>
>To: Greg Aldering <aldering@panisse.lbl.gov>
>cc: hstsearch@lbl.gov
>Subject: Re: Host galaxy for acs04-076 (aka Zamorano)
Hi Greg
At relatively high redshifts (z > 1), trying to match colors and observed
morphologies is often mis-leading. Any interpretation of the type
of galaxy, based on its colors at these redshifts are not satisfactory.
What we do here is to say that a "local" elliptical SED, once shifted to
the redshift of this object, gives the best fit to its observed SED. This
will then be interpreted as the progenitor of local elliptical at z=1.5.
Of course, if you include dust in your SED, you might get a similar result
using a starburst SED. THis is the famous redshift-dust degeneracy
in estimating spectra type and redshift of objects. I guess you need the
type
to identify if the host galaxy is an elliptical and hence, if the Sne is
Type Ia. For this purpose, it may be better to use the Sne color as a
diagnostic.
The photometry and redshift quoted is for both the objects, although it
looks as double nuclei. The point is that we are here looking at the ACS
data where we see the two nuclei. However, on the ground-based infrared
data, which is combined with the ACS, we only see one object due to its
lower resolution. We convolve the ACS with the ground-based psf when doing
the photometry and hence, objects like this will be considered as a single
galaxy. the alternative is to use the ACS data alone without the
supporting subaru and near-IR data. However, for objects at z > 1, the
absence of NIR data will cause problem.
cheers
Bahram
****************************************************************************
* * *
* Bahram Mobasher * Phone: (410) 338 4974 *
* Space Telescope Science Institute * *
* 3700 San Martin Drive * fax: (410) 338 5090 *
* Baltimore MD 21218 * *
* USA * email: mobasher@stsci.edu *
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On Mon, 5 Apr 2004, Greg Aldering wrote:
>
> Hi Bahram,
>
> We where just looking at the host galaxy for Zamorano, for which you
> quoted E-galaxy colors and z = 1.6. On the ACS 2003 coadditions there are
> clearly two nuclei and the hints of spiral arms. (See object in the center
> of the attached PS file.) Is this the same galaxy that you typed? In your
> experience, how often do you get an early spectrum for objects which are
> morphologically not early type galaxies (in the restframe UV)?
>
> Also, could you send the phot-z for Pine? We seem to be missing it
> according to Saul.
>
> Thanks!
>
> Greg
>
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