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Euclid: the selection of quiescent and star-forming galaxies using observed colours


L. Bisigello

C.J. Conselice

S. Andreon

M. Bolzonella

P-A Duc

B. Garilli

A. Humphrey

C. Maraston

M. Moresco

L. Pozzetti

C. Tortora

G. Zamorani

N. Auricchio

J. Brinchmann

V. Capobianco

J. Carretero

F.J. Castander

M. Castellano

S. Cavuoti

A. Cimatti

R. Cledassou

G. Congedo

L. Conversi

L. Corcione

M.S. Cropper

S. Dusini

M. Frailis

E. Franceschi

P. Franzetti

M. Fumana

F. Hormuth

H. Israel

K. Jahnke

S. Kermiche

T. Kitching

R. Kohley

B. Kubik

M. Kunz


S. Ligori

P.B. Lilje

I. Lloro

E. Maiorano

O. Marggraf

R. Massey

D.C. Masters

S. Mei

Y. Mellier

G. Meylan

C. Padilla

S. Paltani

F. Pasian

V. Pettorino

S. Pires

G. Polenta

M. Poncet

F. Raison

J. Rhodes

M. Roncarelli

E. Rossetti

R. Saglia

M. Sauvage

P. Schneider

S. Serrano

A. Secroun

F. Sureau

A.N. Taylor

I. Tereno

R. Toledo-Moreo

L. Valenziano

Y, Wang

M. Wetzstein

J. Zoubian


The Euclid mission will observe well over a billion galaxies out to z ∼ 6 and beyond. This will offer an unrivalled opportunity to investigate several key questions for understanding galaxy formation and evolution. The first step for many of these studies will be the selection of a sample of quiescent and star-forming galaxies, as is often done in the literature by using well-known colour techniques such as the ‘UVJ’ diagram. However, given the limited number of filters available for the Euclid telescope, the recovery of such rest-frame colours will be challenging. We therefore investigate the use of observed Euclid colours, on their own and together with ground-based u-band observations, for selecting quiescent and star-forming galaxies. The most efficient colour combination, among the ones tested in this work, consists of the (u − VIS) and (VIS − J) colours. We find that this combination allows users to select a sample of quiescent galaxies complete to above ∼70 per cent and with less than 15 per cent contamination at redshifts in the range 0.75 < z < 1. For galaxies at high-z or without the u-band complementary observations, the (VIS − Y) and (J − H) colours represent a valid alternative, with >65 per cent completeness level and contamination below 20 per cent at 1 < z < 2 for finding quiescent galaxies. In comparison, the sample of quiescent galaxies selected with the traditional UVJ technique is only ∼20 per cent complete at z < 3, when recovering the rest-frame colours using mock Euclid observations. This shows that our new methodology is the most suitable one when only Euclid bands, along with u-band imaging, are available.


Bisigello, L., Kuchner, U., Conselice, C., Andreon, S., Bolzonella, M., Duc, P., …Zoubian, J. (2020). Euclid: the selection of quiescent and star-forming galaxies using observed colours. Monthly Notices of the Royal Astronomical Society, 494(2), 2337-2354.

Journal Article Type Article
Acceptance Date Mar 12, 2020
Online Publication Date Apr 7, 2020
Publication Date May 11, 2020
Deposit Date Apr 23, 2020
Publicly Available Date Apr 23, 2020
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 494
Issue 2
Pages 2337-2354
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL
Publisher URL
Additional Information This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society©: 2020 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


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