1. CO/[CII] Tomography with the Large Submillimeter Telescope
focus on feasibility study, just want to encourage discussions on sciences using the sample.
Yoichi Tamura (IoA, UTokyo)
Ryohei Kawabe, Kotaro Kohno, Tai Oshima and LST WG
The 3rd WS on Large Aperture Sub/mm Telescopes in the ALMA Era (LSTWS2015)
NAOJ Mitaka, March 10-11, 2015

2. Outline
Introduction
What is the parameter space to go with single dish (SD) telescopes?
How do SD telescopes complement ALMA?
CO/[CII] Tomography: Imaging-spectroscopic survey with LST
Feasibility study / science requirements
Possible science cases
Submm transients
Just show the expected sensitivity
Summary

3. Cosmological volume & time
New discovery space?
Depth
Spectral coverage
Spectral resolution
Cosmological volume & time
Angular resolution
Wide field
Polarization

4. Noise level achieved with SD telescopes
How can bolometer cameras on SD compare with ALMA?
270 GHz (1.1 mm) sensitivity
(scaled from AzTEC/ASTE)
1-sigma noise level as a function of diameter of primary reflector (i.e. diffraction limit and collecting area) and the no. of bolometer pixels (i.e. mapping speed)
The sensitivity is always limited by photon (Background) and confusion noises.
ALMA/Band 6 requires 1.2 million pointings!
5x more sensitive
than ALMA
2x more sensitive
than ALMA
comparable to ALMA

5. Why SD + camera?
Single dish telescopes equipped with a large-format (> 1 kilo-pix) bolometer camera always exceeds ALMA in sensitivity when we map > 1 deg2 region.
Deg2 scale survey will reach the confusion limit in a reasonable survey time ( hrs).
Awarding >100 hr of ALMA time is not realistic...
The μm bands provide a unique and uniform window to high redshift universe (z > 1, even z ~10).
For those reasons, bolometer cameras operating at ~1 mm on ground- based single dish telescopes have often been employed for wide-field deep survey for distant galaxies.

6. HerMES Lockman Hole
© HerMES / ESA
4 deg

7. Motivation
SMG surveys always suffer from difficulties in measurements of redshift, one of the most fundamental quantities.
Redshift measurements depend on optical spectroscopy.
SMGs are too dusty to detect rest-UV/optical lines.
Sub/mm spectral scan is time-consuming.
Why don’t you try to survey mm/submm lines from the beginning?
Multi-transition CO search will benefit from negative K-correction.
Mm/submm lines do not suffer from extinction by gas and dust.
Clearly, the important next step is spectroscopy, in order to determine the redshifts
But we always suffer from this

8. This is a light-cone of star-forming galaxies from redshift 0 to 10, which are fully simulated from SAM and the Millennium Simulation.

9. CO/[CII] Tomography LST Beam
Arp 220 model
(Carilli et al. 2011, Astron. Nachrichten.)
Cloverleaf QSO at z=2.6
(Bradford et al. 2009, ApJ, 705, 112.)
CO/[CII]: representative emission lines in mm-FIR.
Benefit from negative k-correction of CO ladder and FIR lines. Overcome the confusion problems.
CO in SMGs w/ NRO45m
(Iono et al. 2012, PASJ)
By searching CO/CII in those galaxies we will be able to map out the 3d distribution of star-forming galaxies. This is what we call ‘co/c+ tomography’.
One of the unique points is the survey can benefit from bright emission lines such as CO/[CII], which are representative emission lines in mm-FIR.
This allows us to split blended galaxies in redshift space, and thus break the confusion limit.
Also it benefits from the negative k-correction because stronger/higher-J CO or FIR fine-structure lines are redshifted into the observing bands, which offers the window to high-z universe.
LST will be able to construct 100,000 galaxy sample with spectroscopic redshift, using a large-format imaging spectrometer. Our feasibility study shows we will detect 100,000 galaxies, including ~100 z > 8 sources.
This 3-dim survey which we call “CO/[CII] tomography”
LST Beam

10. Large Submm Telescope LARGE APERTURE (D = 50 m)
WIDE FIELD OF VIEW (Φ = 0.8 deg)
LONG-SUBMM/MM FREQUENCY BAND
SURVEY-ORIENTED
(Endo et al. 2011)

11. Sensitivity-Limited Survey with LST
Sensitivity-limited survey with a future large aperture telescope
50 m single dish. (cf. Kawabe-san’s talk)
100 pix, dual-pol. receiver array which simultaneously covers the GHz wavebands.
t(on-source) = 1000 hr (~several months)
Area = 2 sq-deg
extracting galaxies with at least 1 line detected at >5σ.
Assumptions
Tsys (PWV, Treceiver, ηaperture): same as the ALMA median condition.
scaling a result from the Nobeyam 45m OTF calculator (Sawada+2008)
Parent sample (retrieved from the S3-SAX/MySQL webpage)
1.4M objects with SCOΔV ≧ 0.01 Jy km/s for all transitions up to J =10 from the “MilliMillennium Simulation” (1/64 of the full simulation)
Let’s consider feasibility study on a sensitivity-limited survey

12. Sensitivity-Limited Survey with LST
The depth achieved in the 2 deg2 survey is comparable to that obtained in a 1-hr full ALMA observation, but the survey area is ~13000 times larger than the ALMA FoV at 3 mm.
The survey can detect the MW-like galaxies at z ~ 2.
cyc1 (Nant=32), 1.0hr, 5σ = 0.18 Jy km/s (5.5e9Mo)=>Nant=50: 0.18/1.57 ~ 0.11 Jy km/s (3.5e9Mo) => 8hr: Jy km/s (1.2e9Mo)
M(H2) ~ 5e10 Mo
PdBI 10hr
1 Jy km/s →
LST 2 deg2 survey
0.1 Jy km/s →
(R = 1000, i.e., Δv = 300 km/s)
ALMA 1 hr
M(H2) ~ 3.5e9 Mo
M(H2)~1e9 Mo: S3-SAX model limitation

13. Light cone from the LST 2-deg2 Survey
Observer (z=0) ↓
LST
2-deg2 Survey
Comoving distance (h-1 Mpc)
Comoving Y (h-1 Mpc)
z=1
z=2
z=3
z=4
z=5
z=6
z=7
10^5 galaxies across the cosmic time
10^3 galaxies in the epoch of reionization

14. RSD Redshift Space Distortion
Verify GR by estimating the growth rate of structure, dark energy problem
CO/[CII] Tomography
let me show the extragalactic/cosmological science cases that will be doable using the LST.
LSS Cosmic Large-Scale Structure
Investigate the correlation between dark and baryonic matters from clustering analysis, dark matter problem
CSFH Cosmic Star-formation History
Investigate mass/luminosity function of molecular gas as a function of redshift, “hidden” history of baryonic matter
EoR Epoch of Reionization
Search for earliest “hidden” galaxies, first generation galaxies
Evolution of Galaxies
Cosmic evolution of galaxies proved through properties of interstellar medium
... and serendipitous discoveries
Line emitters, transient and variables, ...

15. Outline
Introduction
What is the parameter space to go with single dish (SD) telescopes?
How do SD telescopes complement ALMA?
CO/[CII] Tomography: Imaging-spectroscopic survey with LST
Feasibility study / science requirements
Possible science cases
Submm transients
Just show the expected sensitivity
Summary

16. New discovery space? Time domain Depth Spectral coverage
Spectral resolution
Time domain
Angular resolution
Wide field
Polarization

17. “Submm flare” from GRB reverse shocks
Earliest afterglows from reverse shocks (< 4 hr) peak at ~300 GHz, and bright (~1 mJy) even at z > 10 (Inoue+2007)
similar to SMGs
Bright compared to a typical galaxy at z > 5 (~10 uJy)
But, short-lived... → Deep and wide image in one shot
ASTE (5σ, 0.5 hr, confusion limited)
LST (0.36 mJy at 1.1mm, 5σ)
1 mJy →
1 uJy →
Predicted SED of GRB afterglow at z = 1–30
4hr after the burst
(Inoue+2007, MN, 380, 1715)

18. z = 30 GRB afterglow (1-12hr, 300GHz)
1.0
LST 50m
ALMA
(mosaic)
ALMA FoV
(Band 7)
Flux density (mJy/B)
5 arcmin
0.0
–0.1
Swift/BAT
error circle
CCAT 25m
ASTE 10m

19. Summary CO/[CII] Tomography Time-domain science in the sub/mm
will aim to open a new discovery space complementary to what current/planed telescopes, such as ALMA, SPICA, Subaru/TMT, and WISH, are exploring/will explore.
will provide a basic dataset useful for extragalactic/cosmological studies (“Submm version of SDSS”).
2-deg2 survey:
LST + multi-beam spectrograph can construct a spectroscopic sample of ~10^5 star-forming galaxies from z = 0 out to the epoch of reionization.
RSD, clustering analysis, cosmic SF history, reionization era, etc.
Time-domain science in the sub/mm
SD telescopes should be powerful for time-domain science