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A multi-band view on the evolution of starburst merging galaxies. Yiping Wang (王益萍) Purple Mountain Observatory, China National Astronomical Observatories of China. In 70 ’ s, a few very luminous infrared galaxies were observed.

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a multi band view on the evolution of starburst merging galaxies

A multi-band view on the evolution of starburst merging galaxies

Yiping Wang

(王益萍)

Purple Mountain Observatory, China

National Astronomical Observatories of China

in 70 s a few very luminous infrared galaxies were observed
In 70’s, a few very luminous infrared galaxies were observed

In 80’s, IRAS satellite gave for the first time a proper census of the infrared emission of galaxies (up to Lir ~10^12 Lsun) at low redshift.

slide3
Emission properties of infrared galaxies

PAH bump

Dust emission

Stellar light

Lagache et al. 2005

slide4
IR Local Luminosity Function:

(Sanders & Mirabel 1996)

IRAS number counts:

(Hacking et al. 1987)

slide5
Spitzer deep surveys could reach LIGs down to redshift z~3.

IRAS 80’s

~100mJy

ISO (late 90’s)

~0.1mJy

Spitzer (now)

~0.01mJy

isocam and spitzer 24um source counts
ISOCAM and Spitzer 24um source counts:

Z<2

Z<0.3

Lagache 2004 model

Papovich et al. 2004

Elbaz et al. 1999

slide7
Nature of local and distant ULIGs:

a) ~100% local ULIGs are merging systems (Kim et al. 2001);

b) >50% high redshift ULIGs give indication of interacting; part of SCUBA sources are suggested to be high redshift counterparts of local ULIGs and LIGs (Smail et al. 1998)

slide8
Morphological study of distant Spitzer galaxies

ACS images in CDF-S/GEMS area (Papovich et al. 2004)

X 2 in the deeper GOODS data

Statistics given by Bell et al. 2005: (z~0.7, 1500 galaxies)

Strongly interacting galaxies <30%

Spiral morphologies >50%

E/S0 morphologies ~20%

slide10
Why do such a model?
  • Statistically understand the role which mergers actually could play in the galaxy evolution studies.
  • Whether ULIGs and LIGs could evolve in a continuous way.
  • Whether density and luminosity evolution could come out naturely and simply.
modelling the infrared burst phase at high z
Modelling the infrared burst phase at high z

1) Mass-light ratio for faint blue starburst galaxies

L/L = ( M/M )^h, L (z) ~ f(z, l0, W0 )

where h = 4/3 (Cavaliere & Menci, 1997)

2) ULIGs from gas rich mergers of high redshift

h =2.8 (an infrared burst phase) (observation and N-body )

3) Differential dimming ~ (L_{ir}/Lc)^ z means the

brighter ones dim faster.

~0.4 at FIR

(Wang & Biermann 2000, Wang 2002)

model fitting of isocam and spitzer results
Model fitting of ISOCAM and Spitzer results:

Franceschini et al. 2001

Perez-Gonzalez et al. 2005

AGN?

slide14
Cosmic star formation history associated with accretion based on X-ray deep surveys (Wang et al. 2003)
constraints from spitzer vla deep surveys
Constraints from Spitzer & VLA deep surveys:

Barger et al. 2000

Cowie et al. 2004

conclusions
Conclusions:

1)A population of LIGs or ULIGs triggered by galactic

interactions at z~1 could successfully account for the upturn of

IRAS, ISO, Spitzer and VLA number counts at faint flux level.

.

2)The decrease of merger rate with cosmic time alone is not

sufficient for such strong evolution, an infrared burst phase is

crucial for the steep slope of the ISO and Spitzer differential

counts at sub-mJy.

3)Dusty starburst galaxies triggered by galactic interactions at

z~1 would contain about 30%~50% of the stellar mass in the

Universe, Comparing with the NIR deep surveys and the

background measurements.

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