Scuba-2 Ultra Deep Imaging EAOSurvey (STUDIES):
Number Counts and Counterpart properties
Speaker: Chen-Fatt Lim (ASIAA & NTU, Taiwan)

STUDIES group(136 members from Canada, China, Korea, Japan, United Kingdom, Taiwan, etc)

Introduction

Dole et al. 2006

Reviews by Casey et al. 2014

Introduction

Hopkins et al. 2008!

The IR luminosity is correlatedwith high SFRs and major mergers!

Dust particle re-radiates the lightat IR/sub-mm during the (U)LIRG
phase!

(U)LIRG phase is believed to be
short-lived (~200 Myr)!

Do the major mergers dominate
cosmic star formation at early
universe?

JCMT SCUBA-2!
!
!

Scanning 450 and 850 µm images simultaneously
7.9” and 15” spatial resolution @ 450 and 850 µm
450 µm observation is sensitive with the water vapor

Image Credit: William Montgomerie

SCUBA-2 Ultra Deep Imaging EAO Survey(STUDIES)!
!
!

An EAO JCMT Large Program
Under the best weather condition (𝛕225GHz < 0.05)
STUDIESooSTUDIES-COSMOS (330 hr, 2015-2018)
STUDIES-SXDS (320 hr, 2017-2020)!

Daisy scan mode in each field(D = 3’ ultra-deep core; D = 15’ outer region)!

Reach the ~ 0.6mJy confusion noise at 450 µm

Image credit: JCMT website

SCUBA-2 Data
SCUBA-2 data in COSMOS fieldooo

STUDIES-COSMOS (W.-H. Wang et al. 2017) ~ 170 hours
S2CLS (Geach et al. 2013, 2017) ~ 150 hours
Casey et al. 2013 ~ 40 hours!

The deepest 450 µm image ever (rms ~ 0.7mJy)!
!
!

361 (S/N > 3.5 σ) 450 µm sources
143 (S/N > 6.0 σ) 850 µm sources
In total, 400 sources at 450 or 850 µm

Cutoff Images
MIPS - 24 µm

MIPS - 160 µm

SPIRE - 250 µm

SPIRE - 350 µm

SPIRE - 500 µm

SCUBA-2 - 850 µm

VLA - 3GHzLessconfuse

SCUBA-2 - 450 µm

450 µm Number Counts (STUDIES 1st year)

W.-H., Wang et al. 2017

450 µm Number Counts (STUDIES 1st year)

Herschel 500 µm counts is
1.4× too high in flux or 2.5× too high in density
Sources are clustered & poor resolution (~36”) in HerschelW.-H., Wang et al. 2017

450 µm Number Counts (STUDIES 1st year)

Our latest data is 10× deeper than Herschel observation
W.-H., Wang et al. 2017

Counterpart Identification!
!

177 / 400 have VLA - 3GHz
113 / 400 have MIPS - 24 µm counterparts

In total, we have 281 sources have secure opticalcounterpart in the scale of ~ 1”

! 57 have spectroscopic redshift! 224 have photometric redshift! < z > = 1.65 for 450 µm detected sample! < z > = 2.20 for 850 µm detected sample

Counterpart Properties!
!

Our sample represent the massiveend population on SFR-M* relation
Δ sSFR > 1 (starburst galaxies)

Counterpart Properties!

Our nearby sample follow therelation from low-redshiftobservations.

!

Dotted-dashed lines show thegrey body relation in different
sizes (1-3kpc)!

Detect the majority of LIRG
class galaxies (LIR~ 1011L⊙) atz<2IR Luminosity Function
C. Gruppioni et al. 2013
(Herschel PEP/HerMES)
B. Magnelli et al. 2013
(Herschel PACS)
M. P. Koprowski et al. 2017
(SCUBA-2 850 µm)!

Herschel-based LFs slightly overpredict the number density at thebright-end!

Our results is inconsistent withthe SCUBA-2 850 µm based LFs(selection bias)

Summary!

We obtain the deepest 450 µm image ever (rms ~ 0.7 mJy)!

Our latest data is 10× deeper than Herschel observations!

We are able to detect nearly all LIR > 1012 L⊙ galaxies at most redshifts and the majority of
LIR > 1011 L⊙ galaxies at z < 2!

Our sample might only represent the massive and luminous extension of the galaxy main
sequence!

The Herschel-based LFs slightly over predict the number density at the bright-end

Thank youIntroduction

Pope et al. 2006

Introduction

Pope et al. 2006

Counterpart Properties!

LIR/LUV(IRX) v.s. UV-slope (β)!

IRX-β relation for SMGs
claimed to be uncorrelated!

Blue in β: IR and UV emission
is decoupled(spatially disassociation)

Counterpart Properties!

Assume that the radioemission is coming from thesame region as IR emission!

Compare the radio and UV
flux peak coordinate!

The un-correlation in IRX-β
may not be simply explainedby spatial disassociation