Euclid Science Investigation:
I am the P.I. of one of the 3 U.S. teams working on the European Space Agency's Euclid mission scheduled for launch in Dec 2020 (pushed back to June 2022). The primary goal of Euclid is to measure the properties of dark energy, particularly its evolution over cosmic time through weak-lensing of galaxies, baryon acoustic oscillations and other cosmological tracers. Euclid has an approximately 6 year mission lifetime and so our analysis will continue until 2028.

Members of this investigation are:
Daniela Calzetti (Univ. of Mass., Amherst)
Ranga Ram Chary (IPAC/Caltech)
Kyle Finner

Past members are:
Andrew Battisti (Univ. of Mass., Amherst, now at ANU)
Alessandro Rettura (IPAC/Caltech, now at Keck Observatory)
Bomee Lee (IPAC/Caltech)

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.

The title of our NASA-funded investigation therefore is:
"Precision Studies of Galaxy Growth and Cosmology Enabled Through a Physical Model for Nebular Emission"

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.

  • AAS Jan 2013 (Chary)
  • Euclid Consortium Meeting, Leiden, May 2013
  • Euclid Consortium Meeting, Marseille, May 2014 (Galaxy Evolution SWG)
  • AAS Jan 2015 (Calzetti)
  • Euclid Consortium Meeting, Lausanne, June 2015 (talks in the OU-PHZ and Survey-design session)
  • AAS Jan 2016 (Chary)
  • AAS Jan 2017 (Chary)
  • AAS Jan 2018 (Chary)
  • Euclid Weak Lensing SWG 2018 (Chary)
  • AAS Jan 2019 (B. Lee)

  • "Estimating Astrophysical Sky Backgrounds for Euclid: Implications for the Sensitivity and Surface Density of Galaxies in the Wide Area Survey", A. Rettura & R. Chary, Euclid internal report v1.0, 31 March 2015
  • "Characterizing the Dust Attenuation in Local Star-forming Galaxies", A. J. Battisti, D. Calzetti, R. Chary, 2016, Astrophysical Journal, 818, 13
  • "Characterizing Dust Attenuation in Local Star-forming Galaxies: Near-infrared Reddening and Normalization", A. Battisti, D. Calzetti, R. Chary, 2017, ApJ, 851, 90
  • "Characterizing Dust Attenuation in Local Star-forming Galaxies: Inclination Effects and the 2175 A feature", A. Battisti, D. Calzetti, R. Chary, 2017, ApJ, 851, 90
  • "Mass-Richness Relations for X-Ray and SZE-selected Clusters at Redshift of 0.4-2.0 as Seen by Spitzer at 4.5 microns", A. Rettura, R. Chary, J. Krick, S. Ettori, 2018, ApJ, 867, 12
  • "Galaxy Ellipticity Measurements in the Near-infrared for Weak Lensing", B. Lee, R. Chary, E. L. Wright, 2018, ApJ, 866, 157
  • "Improved photometric redshifts for future wide-area surveys", B. Lee, R. Chary, 2020, MNRAS, 497, 1935
  • "Revisiting Attenuation Curves: The Case of NGC 3351", Calzetti, D., et al., 2021, ApJ, 913, 37