SXDF-ALMA 2 arcmin2 Deep Survey:Millimeter Line-Emitter SearchNRO-ALMA Science/Development Workshop 2016July 20, 2016Institute of Astronomy, the University of Tokyo D1Yuki Yamaguchi

Today’s outline

• Introduction-Why FIR-to-millimeter emission lines?-Previous studies-Our study

• Observation-Observation field-Observation parameters

• Millimeter line-emitter search-Methods-Results

• Discussion

• Summary

1

Introduction

Burgarella + 2013 Walter + 2013

• The evolution of the cosmic SFRD has been studied-Problems

üWhat is the role of dust-obscured star formation at high-z(especially z > 3-4)?

üWhy the cosmic SFRD decline from z ~ 2 to z ~ 0?ØBecause of declining molecular gas mass density?

p Studying dust-obscured star formation activity at high-zand molecular gas mass density in the universevia FIR-to-millimeter lines is one of the promising tools!

2

De Looze + 2014

• Star formation activities at high-zè [CII] 158 μm line

-A tracer of SFRs-One of the brightest

FIR fine structure lines

• Molecular gas mass density in the universeèCO rotational transition lines

-A tracer of molecular gas mass in a galaxy

• The evolution of [CII] or CO luminosity functionis critical to understand cosmic star formation history

Introduction “FIR-to-millimeter line”

log L[CII] [L⦿]

log

SFR

[M⦿/y

r]

3

Introduction “Previous studies”

Walter + 2014

• Many previous observations are biased

-Follow-up observation of pre-selected sources(e.g., optical/NIR selected galaxies)üBased on stellar mass or star formation properties

è Un-biased searches are needed!

• Un-biased line-emitter searches-Serendipitous detection

üe.g., Tamura + 2014

-CO emitter searches using PdBIüe.g., Walter + 2014

ØDifficult to detect!Velocity [km/s]

Flux

den

sity

[mJy

]

4

Introduction “In this study”

• Un-biased millimeter line-emitter search using ALMA-ALMA is more sensitive than PdBI

ü> 3 times (@ Band 6; ~ 1 mm)üMore efficient search

• SXDF-UDS-CANDELS-ALMA deep survey data-Multi-wavelengths properties of line-emitters

üe.g., redshift, stellar mass

-Constraint on line luminosity function

5

Observation “Field”

• SXDF-UDS-CANDELS field-We can use deep multi-wavelengths images

üe.g., Subaru, HST, VLT, Spitzer, Herschel, JVLA

-The submm galaxy selected by AzTEC/ASTE(Ikarashi PhD thesis)

-There are many star-forming galaxies (e.g., HAEs)AzTEC 1.1 mm SPIRE (HerMES) IRAC (SEDS; SpUDS) Subaru (SXDS)

1.1 mm

250 μm350 μm500 μm

3.6 μm4.5 μm5.6 μm

BVRc

6

Observation “Parameters”• Observation parameters–ALMA Cycle 1 (Band 6; 1.1 mm, 2.0 arcmin2)

• Project ID: 2012.1.00756.S, PI: K. Kohno

–Date: 2014 7/17, 7/18–# of antennas: 30-32–Baseline lengths: 20-650 m–PWV: 0.42-0.55 mm

Credit: NAOJ

7

7

Millimeter line-emitter search “Method”

• We made 3D data cube using CLEAN algorithm- 60 MHz binning (~ 65 km/s @ 275 GHz)- 1σ ~ 0.45-0.70 mJy/beam

• We search for line-emitter candidate with peak S/N > 5using CLUMPFIND (Williams + 1994)

CO(3-2)

CO(4-3)

CO(5-4)

CO(6-5)

CO(7-6)

CO(8-7)

CO(9-8)

CO(10-9)

[CII] 158 µm

8

Millimeter line-emitter search “Results”

Speak = 3.8 ± 0.7 mJy/beam (5.4σ) SΔv = 0.53 ± 0.08 Jy km/s (6.6σ)νobs = 273.29 GHzNo continuum counterpart at 1.1 mm

5σline-emitter

9

Discussion “Line identification”

• Optical-to-NIR counterpart candidate

-Estimation of photometric redshift using SED fitting

10

Discussion “Line identification”

• Optical-to-NIR counterpart candidate

-Estimation of photometric redshift using SED fittingüCO(4-3) emitter @ z = 0.687, if the counterpart is real

ØL’CO(4-3) = (8.3 ± 3.8) × 108 [K km/s pc2]

zphoto = 0.97+0.13-0.40

MW like M82 likeL’CO(1-0)

[K km/s pc2](4.9 ± 2.2)× 108

(0.98 ± 0.44)× 108

Mgas[M¤]

(20 ± 9)× 109

(0.78 ± 0.35)× 109

M★[M¤]

(3.5+5.4-1.0 )

× 108

MWlike:L’CO(4-3) / L’CO(1-0) = 0.17, αCO = 4 M¤ [K km/s pc2]-1M82 like: L’CO(4-3) / L’CO(1-0) = 0.85, αCO = 0.8 M¤ [K km/s pc2]-1

11

Discussion “Molecular gas fraction”

• Molecular gas fraction; fgas = Mgas / (Mgas + M★)- fgas = 0.98 (MW), 0.68 (M82)

• We detect gas rich galaxy with M★ ~ 108.5 M¤

- cf. local dwarf galaxies; M★ ~ 108-9 M¤

• Consistent with the relationfrom Kennicutt-Schmidt law(Popping + 2012)

è the relation is alsosupported from gasobservation

12

Discussion “Molecular gas fraction”

• Molecular gas fraction; fgas = Mgas / (Mgas + M★)- fgas = 0.98 (MW), 0.68 (M82)

• Comparing with semi-analytic models (SMAs)

-Obreschkow + 2009, Lagos + 2012üExtremely gas rich

• CO search with ALMA

-Gas rich galaxywith small M★üThey have been missed

in previous studies

13

Discussion “CO luminosity function”

• Consistent with SAMs-Obreschkow + 2009, Lagos + 2012-Faint end of CO luminosity function is dominated by

main sequence star forming galaxies?

CO(4-3) LF @ z ~ 0.7

14

Discussion “[CII] at z = 5.95?”

• If optical/NIR counterpart is not real…

- [CII] 158 μm @ z = 5.95

• How to confirm?-Spectroscopic observation using ALMA!

üCO(5-4) @ z = 0.687 and [NII] 122 μm @ z = 5.95 can beobserved with only single frequency setup (Band 7)

Observed frequency

CO(5-4) at z = 0.687[NII] 122 μm at z = 5.95

15

16

Summary

• We detect a millimeter line-emitter using SXDF-ALMA2 arcmin2 deep survey data

-CO(4-3) @ z = 0.687-Small stellar mass (M★ ~ 108.5 M¤) and

high molecular gas mass fraction (fgas = 0.98, 0.68)- Luminosity function è Consistent with SAMs

• Confirmation of the detected line

- [CII] 158 μm line @ z ~ 5.95 is also bright-Spectroscopic observation using ALMA

üCO(5-4) @ z = 0.687 and [NII] 122 μm @ z = 5.95 can beobserved with only single frequency setup (Band 7)

17