Chary Team

NASA Euclid Team --- PI: Ranga Ram Chary

Precision Studies of Galaxy Growth and Cosmology Enabled Through a Physical Model for Nebular Emission

Euclid is a 1.2m diameter space-based telescope that takes data in a broad optical band (0.5-0.9 micron) and in three near-infrared bands (y, J and H) spanning 0.9 to 2.0 microns. The data are expected to reach a sensitivity of 24.5 AB mag (10 sigma) in the visible and 24 AB mag (5 sigma) in the near-infrared. Euclid relies on ancillary ground-based data in the UBVRIz bands such that galaxy distances can be measured through accurate photometric redshifts. Euclid requires exceptional photometric precision to ensure that the photometric redshifts can be accurately measured. However, it has been demonstrated that our knowledge of galaxy SEDs is quite poor, particularly at redshifts greater than 1 where the contribution of nebular line emission becomes an increasingly significant part of the galaxy photometry.

Our goals of this investigation are:

  • To use CLOUDY to calibrate nebular line and continuum emission as a function of physical properties of galaxies with spectra from Sloan, VVDS, GOODS (pre-Euclid) and with Euclid+other ground-based spectroscopy surveys during the in flight phase;
  • To calibrate extinction law in galaxies using nebular emission (e.g. Balmer decrement) and UV slope in conjunction with FIR photometry where it exists;
  • To apply the calibration to standard stellar population synthesis models such as BC03 and Starburst99 so that they can be incorporated into phot-z fitting (improvements upon Ilbert et al., Zackrisson et al, Charlot et al.);
  • To work within Galaxies/AGN SWG but integrate analysis methodology into weak-lensing (phot-z) and transients SWG. In particular, we intend to calibrate the dust attenuation law for Type Ia SNe hosts so that the SN light curves can be corrected for extinction accurately.
     

Team Members:

Andrew Battisti (Univ. of Mass., Amherst)
Daniela Calzetti (Univ. of Mass., Amherst)
Ranga Ram Chary (IPAC/Caltech)
Bomee Lee (IPAC/Caltech)