An international team led by researchers from the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL) has discovered one of the brightest non-active galaxies in the early universe.
This galaxy, called BG1429+1202, is located at a redshift of 2.82 and it
is a gravitationally lensed Lyman-Alpha Emitter (LAE) from the Bells
Gallery project.
Although, in general, LAEs are faint, BG1429+1202 is intrinsically very
luminous. Additionally, its flux is
boosted by a factor of about nine by gravitational lensing by a massive
elliptical galaxy in the line of sight at redshift 0.55.
BG1429+1202 was selected for observations using ACAM at the William
Herschel Telescope (WHT) from a large sample of lensed LAE candidates
discovered using the Sloan Digital Sky Survey BOSS spectroscopic
database.
"This is one of the few known cases of galaxies with a very high
apparent brightness and also an intrinsically high luminosity", says
Rui Marques-Chaves, a doctoral student at the IAC-ULL.
To study this system, astronomers applied for a few hours
of Director's Discretionary Time (DDT) at the WHT. They expected to
detect a very bright continuum and Lyman-alpha emission from the blue
features around
the foreground galaxy visible on the Sloan Digital Sky Survey images,
and that's actually what they already saw in the first 15-minute ACAM
spectrum. BG1429+1202 is so bright that it can even
be detected on the photographic images of the Digital Sky Survey.
Motivated by the promising results of the WHT observations, the team
applied for DDT time at the Gran Telescopio Canarias (GTC). Observations
were carried out
just one month after the WHT data were obtained, and provided higher
signal-to-noise imaging and low-resolution spectroscopy of the brightest
lensed features.
Lens modeling of this system revealed the main properties
of the high-redshift LAE. Ismael Pérez-Fournon, from the IAC and ULL and
coordinator of this project says, "Its luminosity and the star
formation rate are
much higher in the rest-frame UV continuum and in the Lyman-alpha line
than in typical LAEs at high redshift. With telescopes such as the GTC
or the WHT we can observe these high-redshift galaxies
because they are gravitationally lensed. If they weren't, then we would
need a future telescope, such as the Extremely Large European Telescope
(E-ELT) or the Thirty Meter Telescope (TMT), to study them in detail."
To select lensed-LAEs like BG1429+1202, astronomers analysed around a
million and a half spectra of galaxies obtained using
the Sloan Telescope. Lyman-alpha emission was detected from galaxies
much further away than their lenses in 187 cases, of which 21 have been
observed with the
Hubble Space Telescope. Those observations confirm that the majority of
these objects are indeed gravitationally lensed.
"Via these same techniques, future data sets from projects such as
WHT/WEAVE and the Dark Energy Spectroscopic Instrument (DESI) will lead
to the discovery of many more types of lensed systems at all
redshifts", concludes Adam Bolton, Associate Director of the NOAO and an
author on this research.
More information:
Rui Marques-Chaves, Ismael Pérez-Fournon, Yiping Shu, Paloma I. Martínez-Navajas, Adam S. Bolton, Christopher S. Kochanek, Masamune Oguri, Zheng Zheng, Shude Mao, Antonio D. Montero-Dorta, Matthew A. Cornachione, and Joel R. Brownstein, 2017, "Discovery of a very bright and intrinsically very luminous, strongly lensed Ly-alpha emitting galaxy at z = 2.82 in the BOSS Emission-Line Lens Survey", ApJL, 834, L18 [ ADS ].
"Discovered one of the brightest distant galaxies so far known", IAC Press Release, 17 Jan 2017.
"17 New Strong Gravitational Lenses Discovered by NAOC Researchers Using HST Data", NAOC Press Release.
Contact:
Javier Méndez
(Public Relations Officer)
More information:
Rui Marques-Chaves, Ismael Pérez-Fournon, Yiping Shu, Paloma I. Martínez-Navajas, Adam S. Bolton, Christopher S. Kochanek, Masamune Oguri, Zheng Zheng, Shude Mao, Antonio D. Montero-Dorta, Matthew A. Cornachione, and Joel R. Brownstein, 2017, "Discovery of a very bright and intrinsically very luminous, strongly lensed Ly-alpha emitting galaxy at z = 2.82 in the BOSS Emission-Line Lens Survey", ApJL, 834, L18 [ ADS ].
"Discovered one of the brightest distant galaxies so far known", IAC Press Release, 17 Jan 2017.
"17 New Strong Gravitational Lenses Discovered by NAOC Researchers Using HST Data", NAOC Press Release.
Contact:
Javier Méndez
(Public Relations Officer)
Source: Isaac Newton Group of Telescopes
