Large surveys of dusty galaxies at high redshift with
AtLAST

Guilaine Lagache, Matthieu Bethermin

► To cite this version:

Guilaine Lagache, Matthieu Bethermin. Large surveys of dusty galaxies at high redshift with AtLAST. Atacama Large-Aperture Submm/mm Telescope (AtLAST), European Southern Observatory, Jan 2018, Garching, Germany. 10.5281/zenodo.1159045. [hal-02271064](https://HAL Id: hal-02271064)

https://amu.hal.science/hal-02271064

Submitted on 26 Aug 2019

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Distributed under a Creative Commons Attribution 4.0 International License
# Large surveys of dusty galaxies at high redshift with AtLAST

Guilaine Lagache & Matthieu Béthermin
LAM
# The high-redshift dusty Universe

* Final frontier in piecing together a coherent picture of cosmic history relates to the period $6<z<15$

* Earliest stars and galaxies began to shine

* The intergalactic medium transitioned from a neutral to a fully ionized gas

* The two are connected (e.g., Planck collaboration 2016, Robertson+2015)

* Another remarkable result :

* Realization that the SFR at redshifts $z>1$ is higher than at present by about an order of magnitude

* $>\frac{1}{2}$ of the energy produced since the surface of last scattering has been absorbed and reemitted by dust (in Dusty Star-Forming Galaxies, DSFG)

<figure><img src="image_2.png" /></figure>
# The high-redshift dusty Universe

* Two fundamental questions AtLAST has to address:

* What is the contribution of the dust-enshrouded star formation at $z>3$?

* What is the role of DSFG in shaping the reionization?

* In particular:

* When did the Universe produce dust? What is the history of star formation?

* How the ISM in typical galaxies matures from a nearly primordial, dust-free state at $z\sim8$ to the dust- and metallicity-enriched state observed at $z\sim4$?

* From gas to stars: what are the processus of regulation of star-formation?
# Observing the high-redshift dusty Universe

* Continuum: $L_{IR}$ (SFR), dust mass, dust temperature

* Lines CII, OIII, NII, OI, CI, CO (and many others...)

* Redshifts

* Gas mass reservoirs

* Gas cooling rate

* Metallicities

* Shocks & AGN activity

<table><tr><td>CII<sub>158</sub></td><td>PDRs, diffuse HI, diffuse ionized gas, HII regions</td></tr><tr><td>OI<sub>63</sub></td><td>Warm and/or dense PDRs</td></tr><tr><td>OIII<sub>88</sub></td><td>High-excitation ionized gas</td></tr><tr><td>NII<sub>122,205</sub></td><td>Low-excitation ionized gas</td></tr><tr><td>CI<sub>370, 609</sub></td><td>Cold molecular gas</td></tr><tr><td>CO</td><td>Molecular gas</td></tr></table>

* Clustering (lines or continuum):

* How galaxies populate dark-matter halo?

* What is the typical halo mass scale of star formation?

* Role of the cosmic web in shaping galaxy properties
# Observing the high-redshift dusty Universe

* In the (sub-)mm, galaxies are so faint and numerous, compared to the angular resolution achievable, that confusion plagues observations substantially.

* Limited to the brightest galaxies

* Béthermin+2017: clustering + low-angular resolution:

* Number counts measured by Herschel at 350 and 500µm between 5 and 50 mJy are biased towards high values by a factor ~2

* Blind surveys with the ALMA interferometer can see fainter DSFGs but are detecting only a handful of galaxies at $z>4$ because of its limited mapping speed.

=> High mapping-speed continuum and spectroscopic galaxy surveys with a large single-dish telescope
Confusion-limited survey with a 25-m dish at 350 microns

* Confusion noise = 105 µJy RMS
  (after excluding 5σ sources)

* This corresponds to a SFR-limit of:
  9 M⊙/yr at z=2
  30 M⊙/yr at z=4
  92 M⊙/yr at z=6
  (for >5σ detections)

* BUT, very hard to reach confusion
  limit on large patches at this
  wavelength
  AND not optimal at z>4

<figure><img src="image_3.png" /><figcaption>Simulation assuming a 25-m and no
instrumental noise</figcaption></figure>

-> some blending, but easy to distinguish
most of individual sources
How size impacts the confusion level?

850 microns

Simulation assuming a 25-m and no instrumental noise

<figure><img src="image_4.png" /></figure>

From SIDES simulations (Bethermin+2017)
How size impacts the confusion level?

850 microns

Simulation assuming a 30-m and no instrumental noise

<figure><img src="image_5.png" /></figure>

From SIDES simulations (Bethermin+2017)
# How size impacts the confusion level?

850 microns

Simulation assuming a 40-m and no instrumental noise

<figure><img src="image_6.png" /></figure>

From SIDES simulations (Bethermin+2017)
# How size impacts the confusion level?

850 microns

Simulation assuming a 50-m and no instrumental noise

<figure><img src="image_7.png" /></figure>

From SIDES simulations (Bethermin+2017)
# SFR limit versus telescope size (for a 850 µm survey)

* Negative K-correction: similar SFR limit for z=2-6.

* From 25m to 50m: confusion limit 5 times lower.

* 40-50m: able to detect the obscured SFR of the typical LBGs (a few tens of $M_\odot$/yr)

<table><thead><tr><th></th><th>25 m</th><th>30 m</th><th>40 m</th><th>50m</th></tr></thead><tbody><tr><td>1σ confusion µJy/beam</td><td>152</td><td>107</td><td>57</td><td>32</td></tr><tr><td>5σ SFR limit at z=2 (M<sub>☉</sub>/yr)</td><td>80</td><td>56</td><td>30</td><td>17</td></tr><tr><td>5σ SFR limit at z=6</td><td>108</td><td>76</td><td>40</td><td>22</td></tr></tbody></table>
Comparison with current single-dish surveys

* z≤3: 350 µm at confusion is spectacular
  => ~3-10 times deeper than mid-IR with Spitzer and much more direct tracer of SFR

* z≥3: 850 µm is the best channel
  - if 50 m: 5 times deeper than NIKA2 and 20 than S2CL

- if 25 m: depth of NIKA2,
but the strength might be the
mapping speed

<figure><img src="image_8.png" /></figure>
Resolved fraction of the SFRD at the confusion

* ≥40m at 850µm: galaxies detected at >5σ explain >50% of the SFRD up to z~6

* A 25m at 350µm, ~85% of the SFRD at z≤2, but the fraction decreases dramatically above.

<figure><img src="image_9.png" /></figure>
# 2D and 3D intensity mapping

* Large-scale spatial fluctuations on the collective emission from all the sources emitting in one frequency band (2D) or in some convenient spectral lines (3D)

* 2D: Cosmic Infrared Background anisotropies

* Herschel and Planck (Viero+13, Planck collaboration +11, +13)

* Problem of degeneracies as N(z) is unknown, hard to isolate the high-redshift signal

* 3D: bright lines (HI, CO, Lya, CII)

* Redshift information is retained ($\delta v \sim 1$GHz)

* Low-angular resolution redshift surveys (confusion limited)

* CII: one of the brightest emission lines in the spectra of galaxies, extinction free tracer of star formation, redshifted into the relatively transparent sub-millimeter and millimeter atmospheric windows for $4 < z < 9$
# CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn epoch)

* **Focal plane:**
  * KIDS, following the success of the NIKA2 IRAM camera

* Cooled to 150 mK thanks to a closed-circle 3He-4He dilution cryostat

* FOV D~15', fλ sampling => two arrays of 1,500 pixels

* Frequency range: (150)200 - 360 GHz

* **Martin-Puplet interferometer** (like a Michelson interferometer but with a movable mirror)
  * Spectral resolution (v/δv): R=100 to 300

* At least one spectrum for all pixels of the matrix every second

* **CONCERTO @ APEX:** θ=20" for CII at z=5

* **Primary goal:** CII intensity mapping and CII-bright emitting galaxy luminosity function at 4.5<z<8.5 + CO intensity mapping at z<2

* But rich ancillary science, from the ISM of our Galaxy to the hot gas and velocity flows in galaxy clusters

* Testing the pathfinder (KISS instrument) and recent funding to quick start the instrument building
# AtLAST lines survey

<figure><img src="image_10.png" /><figcaption>## CII luminosity functions at z~5-6</figcaption></figure>

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>

<figure><img src="image_13.png" /><figcaption>## CO luminosity function at z=1.5</figcaption></figure>
# AtLAST lines survey

## Low frequencies

<figure><img src="image_14.png" /></figure>

Chajnantor

pwv:1mm

zCO=1.3

zCII, NII, OI=6.0

zCI=1.8
# AtLAST lines survey (high frequencies)

## High frequencies

<figure><img src="image_15.png" /></figure>

Chajnantor

pwv:1mm

zCO=0.5

zCII, NII=1.8

zOIII, OI, NIII=4.6
Conclusion

❖ Cover large areas, high mapping-speed (large FOV ~1 deg)

❖ Continuum surveys:

❖ z<3: 350 µm, D>25m, θ<2.5", confusion 1σ<105 µJy/beam

❖ z>3: 850 µm, D>40m, θ<5.3", confusion 1σ<57 µJy/beam

❖ obscured SFR of the typical LBGs at z=6!

=> High redshift dusty Universe: simultaneous 750µm, 850µm, 1.1mm, 1.3mm imaging

❖ Line surveys: Cover a wide frequency band

❖ ex: CII luminosity function at z>4 and CII in reionisation

❖ 1σ = 10⁶ L☉ at z=7 => S δv = 0.8 Jy km/sec

❖ @238 GHz (i.e. CII at z=7)

❖ R=750 => δz=0.01 & δv=400 km/sec