[Paper Review] The Herschel-SPIRE Legacy Survey (HSLS): the scientific goals of a shallow and wide submillimeter imaging survey with SPIRE

Asantha Cooray, Steve Eales+248 more|arXiv (Cornell University)|Jul 20, 2010

Astronomy and Astrophysical Research45 references3 citations

TL;DR

The Herschel-SPIRE Legacy Survey (HSLS) proposes a shallow, wide submillimeter survey covering 4,000 square degrees at 250, 350, and 500 µm to detect 2.5–3 million galaxies down to 26, 27, and 33 mJy, respectively, with a focus on high-redshift sources (z > 1 for two-thirds, z > 2 for one-third, and ~1,000 at z > 5). It aims to enable cosmological studies, reduce confusion in CMB experiments, identify strongly lensed submillimeter sources for testing general relativity, and map proto-clusters and dust-rich systems at high Galactic latitudes.

ABSTRACT

A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z > 1, one third at z > 2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs.

Motivation & Objective

• To conduct a shallow, wide submillimeter survey across 4,000 square degrees to enable large-scale studies of high-redshift galaxies and dust emission.
• To produce a catalog of 2.5–3 million galaxies with 50% completeness at 26, 27, and 33 mJy at 250, 350, and 500 µm, respectively.
• To reduce confusion in cosmic microwave background (CMB) anisotropy measurements by removing point-source contamination from Planck and ground-based CMB data.
• To identify at least 1,200 strongly lensed, bright submillimeter sources for precision tests of general relativity at the 2% level.
• To perform an unbiased survey of star formation and dust at high Galactic latitudes, including debris disks and dust around evolved stars.

Proposed method

• Conduct deep imaging at 250, 350, and 500 µm using the SPIRE instrument on the Herschel Space Observatory over 4,000 square degrees.
• Target the southern celestial hemisphere (3,000 sq. deg.) and an equatorial strip (1,000 sq. deg.) with extensive multi-wavelength coverage.
• Use source extraction and photometry to build a catalog of galaxies with 50% completeness at 5σ confusion limits of 26, 27, and 33 mJy at the three wavelengths.
• Apply statistical and photometric techniques to model and subtract point-source confusion in CMB data from Planck and ground-based experiments.
• Use strong gravitational lensing models to identify and characterize bright, highly magnified submillimeter sources.
• Perform spatial clustering and environmental analysis on candidate proto-cluster regions at z ≈ 2 to study environmental dependence of star formation.

Experimental results

Research questions

• RQ1 What is the distribution and redshift evolution of submillimeter-bright galaxies across 4,000 square degrees?
• RQ2 How many strongly lensed submillimeter sources can be identified, and can they be used to test general relativity at the 2% level?
• RQ3 What is the environmental dependence of star formation in high-redshift proto-clusters at z ≈ 2?
• RQ4 What is the census of dust-rich systems, including debris disks and dust around AGB stars and white dwarfs, at high Galactic latitudes?
• RQ5 To what extent can point-source confusion in CMB experiments be mitigated using deep submillimeter imaging?

Key findings

• The survey is expected to detect 2.5 to 3 million galaxies, with 66% at redshift z > 1 and 33% at z > 2, including approximately 1,000 sources at z > 5.
• The survey will achieve 50% completeness at 26 mJy (250 µm), 27 mJy (350 µm), and 33 mJy (500 µm), corresponding to 5σ confusion noise levels.
• At least 1,200 strongly lensed, bright submillimeter sources are expected to be identified, enabling a 2% test of general relativity.
• The survey will identify 200 proto-cluster regions at z ≈ 2, allowing for an unbiased study of environmental effects on star formation.
• An unbiased census of dust at high Galactic latitudes will be achieved, including debris disks and dust around evolved stars.
• The survey will significantly reduce point-source confusion in CMB experiments by providing a deep, wide-area submillimeter map for source subtraction.