We present the discovery of two z > 6 quasars, selected as i-band dropouts in the Very Large Telescope Survey Telescope ATLAS survey. Our first quasar has redshift, z = 6.31 ± 0.03, z-band magnitude, zAB = 19.63 ± 0.08 and rest frame 1450Å absolute magnitude, M1450 =-27.8 ± 0.2, making it the joint second most luminous quasar known at z > 6. The second quasar has z = 6.02 ± 0.03, zAB = 19.54 ± 0.08 and M1450 =-27.0 ± 0.1. We also recover a z = 5.86 quasar discovered by Venemans et al., in preparation. To select our quasars, we use a new 3D colour space, combining the ATLAS optical colours with mid-infrared data from the Wide-field Infrared Survey Explorer. We use iAB-zAB colour to exclude mainsequence stars, galaxies and lower redshift quasars, W1-W2 to exclude L dwarfs and zAB-W2 to exclude T dwarfs. A restrictive set of colour cuts returns only our three high redshift quasars and no contaminants, albeit with a sample completeness of ~50 per cent. We discuss how our 3D colour space can be used to reject the majority of contaminants from samples of bright 5.7 < 6.3 quasars, replacing follow-up near-infrared photometry, whilst retaining high completeness.

Carnall, A., Shanks, T., Chehade, B., Fumagalli, M., Rauch, M., Irwin, M., et al. (2015). Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infrared colour selection. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. LETTERS, 451(1), L16-L20 [10.1093/mnrasl/slv057].

Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infrared colour selection

M. Fumagalli
Membro del Collaboration Group
;
2015

Abstract

We present the discovery of two z > 6 quasars, selected as i-band dropouts in the Very Large Telescope Survey Telescope ATLAS survey. Our first quasar has redshift, z = 6.31 ± 0.03, z-band magnitude, zAB = 19.63 ± 0.08 and rest frame 1450Å absolute magnitude, M1450 =-27.8 ± 0.2, making it the joint second most luminous quasar known at z > 6. The second quasar has z = 6.02 ± 0.03, zAB = 19.54 ± 0.08 and M1450 =-27.0 ± 0.1. We also recover a z = 5.86 quasar discovered by Venemans et al., in preparation. To select our quasars, we use a new 3D colour space, combining the ATLAS optical colours with mid-infrared data from the Wide-field Infrared Survey Explorer. We use iAB-zAB colour to exclude mainsequence stars, galaxies and lower redshift quasars, W1-W2 to exclude L dwarfs and zAB-W2 to exclude T dwarfs. A restrictive set of colour cuts returns only our three high redshift quasars and no contaminants, albeit with a sample completeness of ~50 per cent. We discuss how our 3D colour space can be used to reject the majority of contaminants from samples of bright 5.7 < 6.3 quasars, replacing follow-up near-infrared photometry, whilst retaining high completeness.
Articolo in rivista - Articolo scientifico
Quasars: general; Quasars: individual: ATLAS J025.6821-33.4627; Quasars: individual: ATLAS J029.9915-36.5658
English
2015
451
1
L16
L20
open
Carnall, A., Shanks, T., Chehade, B., Fumagalli, M., Rauch, M., Irwin, M., et al. (2015). Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infrared colour selection. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. LETTERS, 451(1), L16-L20 [10.1093/mnrasl/slv057].
File in questo prodotto:
File Dimensione Formato  
slv057.pdf

accesso aperto

Tipologia di allegato: Publisher’s Version (Version of Record, VoR)
Dimensione 308.63 kB
Formato Adobe PDF
308.63 kB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/280397
Citazioni
  • Scopus 69
  • ???jsp.display-item.citation.isi??? 62
Social impact