Studies of the submm galaxy population in ECDFS: LESS, ALESS and zLESS
We make available the multi-wavelength imaging,
spectroscopy and redshift catalogs which has been taken as part of the
sub-mm survey(s) of the Extended Chandra Deep Field South, an
extra-galactic survey field at RA: 03:32 Dec: -27:48. This field has
very low far-infrared backgrounds and good ESO and ALMA visibility and
hence has become one of the pre-eminent fields for cosmological survey
science. In particular, the field has been surveyed by Spitzer at
70-um with MIPS (and associated 24 and 160um observations) as part of
the FIDEL survey (PI: Mark Dickinson), deep Herschel far-infrared
imaging at 250, 350 and 500um and extensive 1.4GHz radio imaging.
This field was surveyed with the LABOCA camera on the
MPIfR/ESO/OSO-owned 12-m APEX
Telescope as part of
the LABOCA ECDFS Submm Survey (LESS). This project used 350-hours
of observing time to map the 0.5×0.5 degree Extended
Deep Field South (ECDFS
field at 870um to a depth of ~1.2mJy (Figure right) to detect 126
sub-mm sources above a significance level above 3.7-sigma. Details
of the survey can be found
This project was led by Ian Smail (ESO co-PI), Fabian Walter (ESO
co-PI) and Axel Weiss (MPI PI). The survey is a collaboration of
around 40 scientists based in Europe and the US: D. Alexander,
E. Bell, F. Bertoldi, C. de Breuck, C. Cesarsky, S. Chapman,
K. Coppin, P. Cox, H. Dannerbauer, J. Dunlop, M. Franx, R. Genzel,
G. Hasinger, R. Ivison, A. Kovacs, K. Knudsen, E. Kreysa, D. Lutz,
V. Mainieri, K. Meisenheimer, K. Menten, A. Omont, P. Popesso,
A. Renzini, H.-W. Rix, E. Schinnerer, N. Foerster, G. Siringo,
A.M. Swinbank, P. van der Werf, C. Vlahakis, N, Brandt,
M. Dickinson, P. van Dokkum & E. Gawiser. More information on this
survey can be found here
Follow-up observations of the 870-um selected LABOCA
sources were carried out using ALMA in Cycle 0 as part of program
2011.0.00294.S. These observations were taken with 16 antennae, have
a spatial resolution of 1" and a typical sensitivity of 0.5mJy r.m.s.
Details of the survey and catalog can be found
in Hodge et al. 2013
The image on the left shows a false-colour K/IRAC-3.6um/ALMA
composite of a suset of the SMGs in the survey.
Movies: Annimations (movies) generated from the data can be
In total, the ALMA maps yield 99 SMGs with precisely located
counterparts, directly pin-pointing the source(s) responsible for the
sub-mm emission to within 0.3", without recourse to statistical
radio/mid-infrared associations. These positions for SMGs has
facilitated a number of studies, with over 25 papers written so far.
These include: the source catalog and multiplicity
(Hodge et al. 2013)
the first high-resolution sub-mm number counts
(Karim et al. 2013)
AGN properties of ALMA SMGs
(Wang et al. 2013)
the far-infrared dust SEDs of ALMA SMGs
(Swinbank et al. (2014)
(Chen et al. 2015)
and the sub-mm properties of colour-selected galaxies
Decarli et al. (2014).
Notibly Simpson et
use the 17-band optical-mid-infrared imaging of the
ECDFS to derive photometric redshifts for the ALESS SMGs, deriving a
median redshift of z=2.5+/-0.2 with a modest, but not dominant
(<25%), tail of 870-um selected SMGs at z>4.
ALESS-SPIRE deblended images and catalogs:
Observations of the
ECDFS have been carried out using the Herschel telescope with PACS and
(Oliver et al. 2012).
Due to the low angular resolution of Herschel, we have exploited the
deep 24-um and radio imaging of this field to deblend the
Herschel/SPIRE imaging in order to extract the far-infrared flux
densities and colours of the SMGs. The resulting catalog(s) also
include the SPIRE 250/350/500 flux densities (or limits) for all
galaxies in the prior catalogs. The procedure used to deblend the
field is is discussed
in Swinbank et al. (2014).
In total, there are 6500 galaxies in the prior
catalog. As an example, the 350-um image, best-fit model and residual
maps for the field are shown on the right.
For the ALMA SMGs that are detected in at least two SPIRE bands, the
median photometric redshift increases with increasing wavelength, with
z=2.3+/-0.2, 2.5+/-0.3 and 3.5+/-0.5 for the 250, 350 and 500-um
peakers respectively. 34 ALESS SMGs do not have a >3-sigma
counterpart at 250, 350 or 500-um, and these SMGs have a median
photometric redshift derived from the rest-frame UV-mid-infrared SEDs
of z=3.3+/-0.5, which is higher than the full ALESS SMG sample;
z=2.5+/-0.2. Finally, the median infrared luminosity and
characteristic dust temperature of the >2mJy SMGs is Log(L/Lo)=12.5
(star formation rate of SFR=300Mo/yr) and Td=32+/-1K. At a fixed
luminosity, the characteristic dust temperature of these high-redshift
SMGs is 3-5 K lower than comparably luminous galaxies at z = 0,
reflecting the more extended star formation occurring in these
systems. These results are discussed in
Swinbank et al. (2014).
Da Cunha et
The deblended 250/350/500-um ECDFS catalog for all ~6500 sources in
the prior catalog is available
All SPIRE images, model fits and residual maps are
from this directory
Finally note that deblended images, maps and catalogs for other
extra-galactic fields (COSMOS, GOODS-N, GOODS-S, SSA22) are also
We were awarded an ESO VLT Large Programme (zLESS -
allocated 250hrs with VIMOS, FORS2 and XSHOOTER) as well as Keck
MOSFIRE and DEIMOS and Gemini GNIRS) to obtain spectroscopy of the
ALESS submillimetre sources.
In Danielson et al. (2016)
we present the spectroscopic redshifts
for 52 of these ALMA SMGs, determining a redshift of z=2.3+/-0.2. The
redshift distribution features a high-z tail, with 23% of the SMGs at
Using the spectroscopic redshifts and the extensive UV-to-radio
photometry in this field, we produce optimised spectral energy
distributions (SEDs; figure left)
the SMGs with spectroscopic redshifts, we derive a median stellar mass
of M*=6+/-1x10^10Msol. By combining these stellar masses with the
star-formation rates measured from the far-infrared (using the
deblended SPIRE catalogs discussed above), >2mJy ALMA SMGs appear to
lie (on average) a factor ~5 above the so-called ``main-sequence'' for
star-forming galaxies at z~2.
As a resource for future SMG studies, the rest-frame SEDs of the ALMA
SMGs from Magphys are made available
. The tarball includes both fits and ascii formats. The physical
parameters, such as stellar masses, dust-reddenning (Av), star formation rates, dust masses and
temperatures and luminosity weighted ages derived from the Magphys SED modelling are also made available in
. If these are
used, please cite Danielson et al. (2016)
zLESS spectroscopic catalogs and data
When designing the slit masks, we also in-filled the slit masks with
other candidate high-redshift galaxies, in particular with mid-,
far-infrared or radio selected galaxies. We provide the redshifts for
all ~2000 galaxies targeted as part of the spectroscopic campaign in
the link below
Download the full spectroscopic catalog here
The one- and two-dimensional spectra for all ~2000 galaxies targetted
(fits and ascii) are also made available:
Download the spectra here
This catalog is organised as: Galaxy ID; RA; Dec; redshift; Quality flag; Instrument; other IDs; notes
zALESS Table Notes:
The ID relates to the input catalog from which a target was selected.
These are summarised
Danielson et al. (2016)
, and details are also (briefly) given
101-500: Statistically Robust or Tentative candidate LESS SMG
counterparts from Wardlow et al. (2011)
but which were later shown by ALMA to be incorrect
IDs by Hodge et al. (2013).
500-700: Robust or tentative IDs for LESS sources with
signal-to-noise of SNR=2.7--3.7-sigma in the original LESS map. These
IDs for ``faint SMGs'' are derived using 1.4GHz radio emission
from Biggs et al. (2011)
but have not yet been confirmed (or ruled out) by ALMA.
700-1000: Galaxies in the LESS error circles which have
photometric redshifts that are consistent with the ALESS SMG photometric
redshifts (Wardlow et al. 2011)
1000-3000: 24+70-um-selected galaxies from the Spitzer FIDEL survey without pre-existing spectroscopic redshifts
from Magnelli et al. (2008).
4000-4300: Chandra X-ray sources from the 2Ms or 4Ms
surveys; e.g. (Luo et al. 2008).
50000-51000: Optically faint radio galaxies (OFRGs) from the
JVLA 1.4GHz survey of this field. These radio sources are typically
brighter than >20uJy at 1.4GHz but have optical magnitudes
fainter than I(AB)=22 (Biggs et al. 2011).
70000-72000: Optically (colour) selected galaxies. These
comprise a mix of z~2 Lyman-alpha emitting galaxies, BM/BX
galaxies and Lyman break galaxies at 1.5 < z < 3.5.
90000-90200: B- or V-band drop-out galaxies (i.e. candidate
z>2.5 or z>3.5 galaxies).
>80000: Galaxies which were not in any of the other catalogs but
which could still be placed on the masks.
Any source in the catalog that is labelled with a "b" suffix denotes a
secondary galaxy that happened to lie on the slit, but is not the
Note that the input catalogs are not unique (a galaxy could be an ALMA
source that is also in the FIDEL 24-um catalog, a radio catalog, a
BX/BM and also a Chandra source). In those instances, the object will
only appear once in the table, but under the ID from which it was
selected for slit placement (i.e. there are no RA/Dec repeats).
However, the "other IDs" column lists those sources which appear in
The instrument IDs are denoted by F=VLT/FORS2, V=VLT/VIMOS,
X=VLT/XSHOOTER, M=Keck/MOSFIRE, D=Keck/DEIMOS, and
The quality flag (Q) for the spectroscopic redshifts is Q=1 for secure
redshifts; Q=2 for redshifts measured from only one or two strong
lines; Q=3 for tentative redshifts measured based on one or two very
faint features; Q=4 for those sources which were targeted but no
redshift could be determined. The redshift distribution for each of
these sub-samples is shown in the figure below.
Comments, questions or requests for
other data to Mark Swinbank; email: email@example.com