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Physics of the Formation and Evolution of Galaxies Report from the High-z Working Group. Tsutomu T. TAKEUCHI (Nagoya University) Hiroyuki HIRASHITA (ASIAA ) Shuichiro YOKOYAMA (Nagoya University) and members of the high- z working group.

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physics of the formation and evolution of galaxies report from the high z working group
Physics of the Formation and Evolution of GalaxiesReport from the High-z Working Group


(Nagoya University)


Shuichiro YOKOYAMA (Nagoya University)

and members of the high-z working group

Japan SKA Workshop 2010, 4-5 Nov., 2010, NAOJ, Mitaka, Japan



  • Part I: Galaxy Evolution with a Wideband Receiver at 1-15 GHz
    • Overview of the Working Group
    • Possible Observations
    • Requirement for the Instruments
    • Summary of Part I
  • Part II: Exploring Non-Gaussianity in the Primordial Perturbation with 21-cm Line Tomography
    • Primordial non-Gaussianity
    • The 21-cm Tomography
    • Summary of Part II

Part I

Galaxy Evolution with a Wideband Receiver at 1-15 GHz


1. Overview of the Working Group

Twenty-twomembers in the mailing list (from students to senior researchers with wide range of expertise).

Representative: Hiroyuki HIRASHITA (ASIAA,Taiwan)

Core members: Tsutomu T. TAKEUCHI (Nagoya U.)

Daisuke IONO (NAOJ)

Shinki OYABU (Nagoya U.)

The high-z working group is open to anyone.

If you would like to participate in this working group, please let us know.


2. Possible Observations

Here we concentrate on a frequency range of 1-15 GHz,possibly contributed from Japanese instrumentation.

H2O maser: 22 GHz (z > 0.5)

NH3lines: 23.7 GHz (z > 0.5)

H I emission line: 1.4 GHz (z < 0.4)

CO absorption lines: z > 6.7


Possible important sciences for lower frequencies:redshifted H I: 1.4/(1 + z) GHz for cosmology (Part II)

In this talk, direct contributions from the WG members are indicated by .


2.1 H2O maser (22 GHz; z > 0.5)

Two detections so far for z > 0.5

Barvainis & Antonucci (2005): SDSS J08043+3607 @ z = 0.66

VioletteImpellizzeri et al. (2008): MG J0414+0534 @ z = 2.64

z = 2.64 (lensed: factor 35)


100 m Effelsberg

n(H2) > 107 cm-3

T > 300 K

associated with AGN

environments (accretion disk or AGN jets)



2.2 NH3 lines (23.7 GHz; z > 0.5)

  • Emission is very weak
  • ⇒Absorption may be better.
  • An example for the detection of absorption for a lensed quasar at z = 0.9 (Henkel et al. 2008)

Level population of various rotational states

⇒We can trace the excitationtemperature.

Interesting viable way to explore the state of the ISM in high-z galaxies.


2.3H I emission (21 cm; z < 0.4)

Baryonic Tully-Fisher relation (BTF) (McGaugh et al. 2000)

Important empirical relation connecting the halo (dynamical) mass and baryon content. Especially important for very late type galaxies (H I-dominated in baryonic content).

HIPASS result (Meyer et al. 2008):

which is steeper than luminosity TF. However, it is still too shallow.

Some recent works showed a possible downward deviation from a single power law.


2.3H I emission (21 cm; z < 0.4)

The “extended” BTF (McGaugh et al. 2010)

The slope becomes steeper from the largest to the smallest structures (clusters: violet symbols, giant galaxies: blue symbols, and dwarf spheroidals: red symbols).

⇒ Possible effect of feedback?

However, gaseous dwarfs are missing on this plot.

Toward lower H I masses!


2.4 CO absorption lines (z > 6.7)

Molecular absorption lines in -ray burst afterglows

Probe of physical and chemical conditions in high-zISM.

1-15 GHz continuum ~ 0.1-1 mJy at tobs~10 days for z = 5-30

t vs. n, Z in protostellar clouds

expected afterglow spectra

Inoue, Omukai, & Ciardi (2007)



2.5 Continuum





Condon (1992)

Synchrotron from supernova remnants

⇒ Related to star formation activity

 > 15/(1+z) GHz is favorable to avoid f-f absorption in dense (> 103cm-3) regions


2.5 Continuum

15 GHz

Potentially interesting area for very young galaxies

Hirashita (2010)


3. Requirement for the Instruments

  • H2O maser: peak 3 mJy (z = 2.64) with lensing factor 35 (VioletteImpellizzeri et al. 2008) → 0.1 mJy
  • NH3 → determined by the continuum level and S/N. Continuum ~ Jy (quasar) and S/N = 100 → 10 mJy
  • H I emission: down to H I mass = 103 M☉(~ baryonic mass of dSph) → at 3 Mpc; 50 Jy (M/103M☉)/(v/10 km-s) (extended)
  • The radio SED models suggest that absorption with  ~ 1 in a GRB can be observed with a Jy-level detection limit.

(5) Radio continuum from galaxies

Expected observed-frame 1.4 GHz flux density for galaxies of various IR luminosities assuming the FIR–radio correlation (qIR = 2.64) is shown (Murphy 2009).

N.B. Cosmic ray electrons lose energy through inverse Compton scattering of the CMB, and nonthermal continuum is strongly suppressed at high-z.

To detect moderate LIRGs at z = 4-10, the detection limit of 10 nJy is required.


Merits of wide frequency range

  • Lines
    • Can trace the evolution along redshift z
    • Can determine the excitation temperature and density (e.g. CO(1-0) and CO(2-1))
  • Continuum
    • Can receive a larger number of photons

N.B. a special imaging technique to deal with a large dynamic range should also be developed.

⇒ Suggestions are welcome!


4. Summary of Part I

  • Working group member is now composed of 22 people but should be expanded.
  • Possible sciences for 1-15 GHz are
    • Lines (H2O maser, NH3 lines, H I, CO; depending on z)
    • Continuum (Radio-FIR relation → collaboration with ALMA)
    • New ideas!
  • Requirements:
    • Sensitivities of m-10 nJy.
    • Imaging techniques should also be developed.

Part II

Exploring Non-Gaussianity in the Primordial Perturbation with 21-cm Line Tomography


1. Primordial Non-Gaussianity

1.1 Basics

CMB, LSS observations

⇒ nature of primordial fluctuations

⇒ physics of the early Universe.

  • amplitude ⇔ energy scale of inflation
  • scale-dependence ⇔ form of the potential ofinflaton
  • statistics⇔ standard inflation scenario?

Current observations predict that the primordial fluctuation has almost Gaussian statisticsas expected from the linear perturbation theory.

Now the primordial non-Gaussianity is hitting the limelight of cosmologists (Komatsu & Spergel 2001, and many others!)


1.2 Parameterization with fNL

Non-Gaussianity is a very broad category and until recently no systematic way to investigate it was known , in spite of enormous theoretical effort made in 90’s.

The situation has dramatically changed by the introduction of the nonlinearity parameter, fNL. The primordial perturbation F is described as

Non-zero fNL gives

Higher order contribution in the power spectrum (2-point correlation function.)

Leading order contribution in the bispectrum (3-point correlation function) !!


Current observational limit from WMAP 7-year data

(central value ~40 …??)

Future CMB observations: Planck

  • Theoretical predictions:
  • Single, slow-roll inflation model (standard inflation scenario)
  • ( = order of slow-roll parameters )
  • Non-slow-roll model, multi-scalar model

2. The 21-cm Tomography

2.1 The 21-cm signal from neutral hydrogen gas

21 cm hydrogen line: 1.4 GHz

⇒ 1.4/(1+z) GHz @redshift z


z = 100 – 30 ⇔ 14 MHz – 47 MHz




Brightness temperature

: spin temperature of H I.

: optical depth for the hyperfine transition.

Fluctuation in the brightness temperature

density fluctuations of neutral gas

primordial fluctuations

Loeb and Zaldarriaga (2004)


2.2 Bispectrum of the CMB temperature fluctuations

The bispectrum (Fourier transformed 3-point correlation) of the CMB brightness temperature map can be used to estimate fNL efficiently (Cooray 2006).

Optimistic prediction

Bandwidth: 1 MHz

Frequency: 14 - 45 MHz

(z ~ 100-30)

Multipole: lmax~ 105

3D data!!

CMB observations


2D data


3. Summary of Part II

  • Non-Gaussianity in the primordial fluctuation is crucial to constrain the type of inflation.
  • The nonlinearity parameter fNLis the key tool to explore the non-Gaussianity. Standard inflation model predicts fNL = O(0.01), while multi-scalar or non-slow-roll inflation scenarios predict fNL >O(0.1).
  • The 21-cm line tomography works as a promising method to determine fNL.If we achieve DfNL ~ 0.01, we can distinguish inflation models finely and constrain plausible scenarios.
  • Many realistic problems remain to be solved. Integrated effort from observational and theoretical side is needed!


TTT has been supported by Program for Improvement of Research Environment for Young Researchers from Special Coordination Funds for Promoting Science and Technology commissioned by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.