dusty star-forming galaxies at z > 4 with ska2 (& ska1)

‘SKA1 Continuum Science Assessment Workshop’ | Sep 10, 2013

Dusty star-forming galaxies at z > 4 with SKA2 (& SKA1)

M. Sargent (U. of Sussex)

with E. Daddi (CEA), M. Béthermin (ESO/CEA)

Sep. 6, 2013 1

Burgarella+ ’13

Statistical characterization of SF-activity

Karim+ ‘11

Smit

+ ‘1

2

The 2-SFM decomposition…

Sargent+ ’12 Distribution of (massive) star-forming galaxies at 1.5 < z < 2.5 w.r.t (s)SFR & M✭ (Rodighiero+ ’11):

Mass-invariant decomposition into 2 log-normal distributions (‘normal’ & starbursting galaxies, resp.).

M. Sargent

z = 2: starburst contribution to SFRD [M⦿/yr Mpc-3]: ~14% (cf. Kaviraj+ ’12)

(If description is extendable to unsampled mass range.)

2 Sep. 6, 2013

Cause(s) & effect: Interpreting the decomposition…

➽ main-sequence activity? ➽ starbursts?

A snapshop at z ~ 2, prior to measuring (s)SFR distributions… Dark matter accretion spec-trum in cosmological simu-lations (Dekel+ ’09; Goerdt+, in prep.): §  smooth accretion

§  clumpy accretion with major mergers in high-MDM tail

.

3 M. Sargent Sep. 6, 2013

Sep. 6, 2013 4

Stellar MF of star-forming galaxies, z < 4: (also: Muzzin+ ‘13, Santini+ ‘12, Ilbert+ ’10, Marche-sini+ ’10, Pérez-González+ ‘08, Fontana+ ’06, …)

Stellar mass function evolution

Ilbert+ ‘13

Evolution of M*& Φ*:

Sep. 6, 2013 5

1) stellar mass fct. of star-forming galaxies

e.g.: Pozzetti+ ‘09

2) SB+MS decompo-sition at fixed M★

Sargent+ ’12

3) redshift-evolution of sSFR of main seq.

e.g.: Reddy+ ’12

IR LFs: pre-Herschel (Sargent+ ‘12)… … & using Herschel (Gruppioni+ ’13)

Jan. 17, 2013

SFR distribution functions…

6

… or equivalently: radio luminosity functions (based on the observed evolution of normal and starburst galaxies; has no ad-hoc tuning or free parameters.)

similar to local 1.4 GHz “monster” and “normal” galaxy split of luminosity fct.

SFR [Msun/yr]

IR number counts (Béthermin+ ‘12):

Sep. 6, 2013 7




Sargent+ ’12


e.g.: Reddy+ ’12

IR SEDs for MS & SBs (e.g. Elbaz+ ‘11)

CIB cross power spectra (Béthermin+ ‘13):

Sep. 6, 2013 8

DM simulations (Pichon, Teyssier)




Sargent+ ’12


e.g.: Reddy+ ’12

Galaxies distributed throughout cosmic web w/ abundance matching

Sep. 6, 2013 9

Predictive power of the empirical 2-SFM approach for high-z star-forming galaxies:

Redshift-distribution of SPT sources (Weiss+ 13)

Redshift-distribution of SCUBA-2 450 um sources (Roseboom+ 13)

Sep. 6, 2013 10

Condon+ ‘12 Béthermin+ ‘12

Source counts…

10 n

Jy

1 uJ

y

flux distribution for star- forming galaxies only

Sep. 6, 2013 11

At what redshifts are these sources?

The higher the flux limit, the harder it gets to any detect high-redshift sources that are not lensed.

Increasing sensitivity does not strongly alter the redshift distribution beyond 10 uJy.

flux cut # z>4 [deg2] # z>6 [deg2] # z>8 [deg2] 100 nJy ~11000 ~610 ~12 10 uJy ~25 ~0.04 ~0.0001

Sep. 6, 2013 12

(Additional advantage of high-freq. coverage up to 14 GHz: detectability of CO at z>9.)

Radio-only, high-z source selection

Mannucci+ ‘10

But…! What if dust emission is essentially absent?

dust-to-radio slope as stand-alone SKA redshift indicator

M. Sargent

Star formation efficiency…

13 Sep. 6, 2013

Karim+ ‘11 Since z = 2.5, main contribution to SFRD has come from M★/M ☉≈ 2×1010 galaxies… (Consequence of 1. const. Schechter M* of stellar mass fct. of SF galaxies 2. const. slope of main seq.)

Integrated Schmidt-Kennicutt law for main seq. galaxies - tight and slightly non-linear:

Sargent+ ’13a

SFE~5-10

SFE~15-30

What causes the increasing SFE of those galaxies that contribute most to the SFR over the last 11 Gyr?

Sep. 6, 2013 14

… and its link to ISM state (e.g. GMC/clump magnetic struct.)

courtesy of A. Cibinel, W. Rujopakarn, M. Pannella

Cases for high-resolution ü  resolved SFR-studies ü  morphological AGN/SF separation

M33: “… galactic fields are dynamically important in the cloud formation process (e.g. Li & Henning ‘11)

dusty star-forming galaxies at z > 4 with ska2 (& ska1)

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