Planck's dusty GEMS: III. A massive lensing galaxy with a bottom-heavy stellar initial mass function at z = 1.5
Journal article, 2017

We study the properties of the foreground galaxy of the Ruby, the brightest gravitationally lensed high-redshift galaxy on the sub-millimeter sky as probed by the Planck satellite, and part of our sample of Planck's dusty GEMS. The Ruby consists of an Einstein ring of 1.4?? diameter at z = 3.005 observed with ALMA at 0.1?? resolution, centered on a faint, red, massive lensing galaxy seen with HST/WFC3, which itself has an exceptionally high redshift, z = 1.525 ± 0.001, as confirmed with VLT/X-shooter spectroscopy. Here we focus on the properties of the lens and the lensing model obtained with LENSTOOL. The rest-frame optical morphology of this system is strongly dominated by the lens, while the Ruby itself is highly obscured, and contributes less than 10% to the photometry out to the K band. The foreground galaxy has a lensing mass of (3.70 ± 0.35) × 1011 M. Magnification factors are between 7 and 38 for individual clumps forming two image families along the Einstein ring. We present a decomposition of the foreground and background sources in the WFC3 images, and stellar population synthesis modeling with a range of star-formation histories for Chabrier and Salpeter initial mass functions (IMFs). Only the stellar mass range obtained with the latter agrees well with the lensing mass. This is consistent with the bottom-heavy IMFs of massive high-redshift galaxies expected from detailed studies of the stellar masses and mass profiles of their low-redshift descendants, and from models of turbulent gas fragmentation. This may be the first direct constraint on the IMF in a lens at z = 1.5, which is not a cluster central galaxy.

Infrared: galaxies

Galaxies: high-redshift

Submillimeter: galaxies

Galaxies: star formation

Galaxies: evolution

Galaxies: stellar content

Author

R. Canameras

University of Paris-Sud

N. Nesvadba

University of Paris-Sud

R. Kneissl

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

M. Limousin

Laboratoire d'Astrophysique de Marseille

R. Gavazzi

Pierre and Marie Curie University (UPMC)

D. Scott

University of British Columbia (UBC)

H. Dole

University of Paris-Sud

B. Frye

University of Arizona

Sabine König

Chalmers, Earth and Space Sciences, Extragalactic Astrophysics

E. Le Floc'H

Centre national de la recherche scientifique (CNRS)

I. Oteo

University of Edinburgh

European Southern Observatory (ESO)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 600 L3

Subject Categories

Subatomic Physics

DOI

10.1051/0004-6361/201630359

More information

Latest update

12/10/2021