LBGs at z1, LIRGs at z1

1
LBGs at z1, LIRGs at z1 the evolution of
Ldust / LFUV with z
Denis Burgarella Observatoire Astronomique
Marseille Provence Laboratoire dAstrophysique de
Marseille In collaboration with Véronique Buat
(France), Emeric Le Floch (USA), Jiasheng Huang
(USA), George Rieke (USA), Tsutomu Takeuchi
(Japan)
2
Introduction
3
Do we live in a dual (UV / IR) Universe ?

• Rest-frame UV e.g. LBGs Rest-frame
  FIR e.g. ULIRGs

SCUBA (Hughes et al. 1998)
Sawicki (2001) The amount of dust in LBGs and
its effect on the inferred SFRs remains
uncertain. It is unlikely that a consensus about
the amount of stellar light intercepted by dust
will be reached on the basis of rest-frame UV and
optical data alone.
4
LBGs form the largest sample of spectroscopically
confirmed high redshift galaxies

• BUT they remain (statistically) undetected in FIR
  and sub-mm
• Knowing more about them means either
• Increasing the size/sensitivity of telescopes
  Herschel / ALMA / Spica to get dust luminosities
• Observing nearer LBGs (say z 1)

5
Wealth of data available(from X-rays to FIR) in
the CDFS
1 '
FUV (GALEX)
NUV (GALEX)
R (COMBO 17)
24 ?m (SPITZER / MIPS)
6
Definition of the 0.9 lt z lt 1.3 LBG sample
IR

• 420 Lyman Break Galaxies in CDF-South
• 15 are detected at 24 um (Red LBGs RLBGs)
• 85 are undetected at 24 um (Blue LBGs BLBGs)

7
Quantitative morphologyMost LBGs are disky

• Morphology extracted from Lauger et al. (05)
  galaxy sample 75 are spirals 22 are mergers 3
  (1) is a spheroid
• Morphology consistent with other works at
  0.6ltzlt1.2 (e.g.Wolf et al. 05, Bell et al. 05)
• Morphology consistent
• with LIRG studies
• (e.g. Zheng et al. 04)

8
Morphology of z 1 LBGs
spiral
spiral
spiral
spiral
spiral
Interacting system
1 arcsec ? 8 kpc _at_ z 1
9
Interesting population of hi-z galaxies

• Blue galaxies
• Dusty galaxies
• Ldust / LFUV 5

VV 114 (Vavilkin et al. 2007)
10
No effect of the InterGalactic Medium at z 1

• This figure from Madau et al. (1996) presents the
  effect of the intergalactic absorption. Magnitude
  increments ?U300 (dotted lines), ?B450
  (short-dashed lines), ?V606 (long-dashed lines)
  and ?U814 (dash-dotted lines), are derived by
  integrating transmission over the corresponding
  bandpass, as a function of the emission redshift.
  Note that below z1.5, there is no noticeable
  absorption.

By detecting LBGs at z1, we want to detect
UV-selected star-forming galaxies
11
UV and IR Data

• UV from GALEX (FUV and NUV)
• IR from Spitzer (IRAC/E-CDFS and MIPS/GTO
  MIPSGOODS)

12
Can we use deep fields (DIS) magnitudes from
GALEX pipeline ?

• Confusion limit
• In deep fields, blending with neighbours can
  give UV magnitudes wrong by up to 1.5 mag
• PSF fitting photometry needed we used DAOPHOT
  valid for point-sources (z gt 0.5 is OK, de Mello
  et al. 2007)

gt 20 beams per source
13
Characterisation of z1 LBGs
14
Luminosities of z1 LBGs

• LFIR estimated from 24 um
• Chary Elbaz (2001)
• Takeuchi et al. (2005)
• LBGs can be LIRGs and even ULIRGs

MIPS GTO limit
15
Comparing LBGs at z1 and at z2

• From Reddy et al. (2006) at z2
• Same range of bolometric luminosity at z1 and
  z2
• SMGs seem to extend RLBG trend

16
The Spectral Energy Distribution of LBGs
from UV to sub-mm.
17
Median SED of Red LBGs
18
Median SED of Blue LBGs
19
SEDs of LBGs _at_ z1 galaxies at _at_ z3 (Forster
Schreiber et al. 2004)
20
SED fitting by Bayesian method

• Rigopoulou et al. (2006)

21

• Blue objects (?RLBG -1.6) can be U/LIRGs
• No major differences (continuity ?) between Blue
  LBGs and Red LBGs
• Similar Optical IR SED (no AGN)
• About the same Star Formation History
• RLBGs more attenuated than BLBGs
• massRLBG gt massBLBG
• UV-optical SED of BLBGs at z1 and LBGs z3
  similar gt high-z LBGs should have a low dust
  attenuation in average

22

• The total Star Formation Rate
• SFRTOT SFRUV SFRIR
• at z 1

23
SFRs vs. SFRTOT
24
z1 LBG Statistics ( 420 LBGs)
At ? 1150Å Ldust gt 1011 Lsun and LUV gt 5 x 109
Lsun gt L L(z1) or 0.1 L(z3)
25
Evolution of Ldust / LFUV with redshift
26
Evolution of the ratio Ldust / LUV vs. the
redshift for UV-selected galaxies
Buat et al. 07 see a decrease in an IR-selected
sample AFUV (z0.7) - AFUV (z0) 0.5 /- 0.1
27
Summary

• The universe is very likely complex
• e.g. from z0 to z1
• Globally IR/UV ?(Takeuchi et al. 05)
• On a galaxy per galaxy basis IR/UV ?

Universe
28
A model for the high redshift universe

• We can conclude that we have two (partially)
  opposite but complementary sides seen in
  rest-frame UV and in rest-frame FIR
• That stresses the need for multi-? surveys

29
Merci / / Thank You
CDFS UV Data from PSF fitting available for
45000 sources Burgarella et al. (2007, MNRAS
380, 986)
30
A dual universe ?
31
Spectral Energy Distribution of Red Lyman Break
Galaxies
32
Spectral Energy Distribution of Blue Lyman Break
Galaxies
33
Akari 15um open time observations of CDFS
OT Akari IRC 15µm (fov complementary to
Teplitzs with Spitzer at the same ?)
Spitzer IRAC 3.6?m
Spitzer IRAC 8.0?m
34
Questions (non exhaustive list)

• Does it exist two completely disjoint galaxy
  samples at high redshift UV ones and IR ones
  in other words, do we see the same universe ?
• If yes, how much do they contribute to the total
  star formation density (redshift dependent ?)?
• What are their physical parameters (mass, Star
  Formation Rate, Star Formation History, Dust
  Attenuation, Metallicity, etc.)
• Could we evaluate the total Star Formation
  Density (SFD) from the UV population and/or the
  IR population (redshift dependent) ?

35
U-dropouts to detect z3 LBGs
36
Summary

• Galaxies at high redshift might appear as
• bright, hot,  sunny  (full of stars) objects as
  in the HST rest-frame UV image of the HDF-North
  (Williams et al. 1996)
• Dark, cold,  shady  (full of dust) objects as
  in the SCUBA rest-frame FIR image image of the
  HDF-North (Hughes et al. 1998)

37
Can we correct LUV to estimate Lbol ?
The amount of dust in LBGs and its effect on the
inferred SFRs remains uncertain. It is unlikely
that a consensus about the amount of stellar
light intercepted by dust will be reached on the
basis of rest-frame UV and optical data alone.
38
The FIR background at z1 (U)LIRGs
Adelberger Steidel (2000)  The analysis of
4 suggested that the bulk of the 850 ?m
background was produced by moderately obscured
galaxies (1 lt Lbol,dust / LUV lt 100) similar to
those that host most of the star formation in the
local universe and to those that are detected in
UV-selected high-redshift surveys. 
LIRGs ULIRGs contribute to 84 of the 140 ?m
extragalactic background light
Elbaz et al. (2002)
39
Can we correct LUV to estimate Lbol ?

• Rest-frame UV and rest-frame FIR cosmic star
  formation densities (SFDs)
• A large fraction of the total SFD lies in the FIR

Pérez-González et al. (2005)
Bouwens et al. (2005)
40
Estimating Ldust from UV

• Adelberger Steidel (2000) detected only a
  (small) handful of LBGs at z3 in the sub-mm. To
  estimate the bolometric dust luminosity, they use
  the method developed by Meurer et al. (1999)
  based on the slope ? of the UV continuum (f? ? ??)

Adelberger Steidel (2000)
UV range (150 - 250 nm)
attenuation -
41
Location of the Lyman break as a function
of the redshift

• LBGs at z lt 3 cannot be selected from
  ground-based imaging

42
Evolution of the UV and FIR star formation
densities at 0 lt z lt 1

• Takeuchi et al.s (2005) GALEX - Spitzer
  analysis suggests
• 80 of ?SFR in FIR at z 1
• 20 of ?SFR in UV at z 1

80
20
43
Dust emission from ?rest-frame 8 ?m

• Ldust is best estimated from the dust emission
  range at ?rf 8 ?m
• Spitzer / 24µm should be used with great care at
  z 2

44
Confusion in Deep GALEX images

• Confusion limit in UV estimated from the
  classical method and from Takeuchi Ishii (2004)
  
• 16 - 20 beams per source
• we need a sophisticated tool for the photometry
  (PSF fitting) we used DAOPHOT (Stetson et al.
  1987) valid for point-sources, z gt 0.5 is OK (de
  Mello et al. 2007)

45
IR-bright LBGs at high z

• Huang et al. (05) 20 of z 3 LBGs is
  detected at 8 ?m and 24?m (ILLBGs)
• Burgarella et al. (06) 20 of z 1
  LBGs is detected at 24?m (RLBGs)
• ? similar percentage of dusty LBGs at z 1 and z
  3

46
More on the sample

• 80 complete down to NUV 26.2
• Redshifts from COMBO 17 (71 complete)
• Total sample 80 complete
• LBG selection UV selection
• ?FUVLBG 0.85 ?FUV _at_ 1800Å

47
Can we correct LUV to estimate Lbol ?

• Spitzer will not observe large sample of
  UV-selected galaxies (e.g. LBGs) at z gt 2
• Herschel will hardly do a better job
• SPICA ?

Huang et al. (2005)
Burgarella et al. (2007)
48
SED _at_ z 1 z 3
49

• Using Data

Using Combined Data
from Recent Telescopes.
50
An introduction to GALEX

• P.I. C. Martin (CALTECH)
• Collaboration US (NASA) Korea France (CNES)
• 50-cm Ritchey-Chretien
• Field of View ? 1.24-deg
• 2 bands far-ultraviolet centered at 150nm
  about 250nm
• Angular Resolution 3-5 FWHM
• Imaging
• Slitless Spectroscopy with a resolution R ? /
  ?? 100 - 200
• Launch on April 28, 2003

51
and its survey mission

• GALEX Early Release Observations released March
  2004 at MAST, the Multi-mission Archive at STScI
• GALEX Release 1 (GR1) data released at MAST
• GALEX Release 2 (GR2) planned for end-2005,
  beginning 2006

52
Morphology and Bulge/Disk Decomposition (by Chen
Zhu)

• Usually, we use the Sersic function to describe
  the surface brightness distribution of galaxies.
  The Sersic function can be expressed in the
  analytical form
• S(r) Seexp K (( r / re)1/n - 1)
• The flexibility of the sersic index,n,allows
  accommodation of exponential disks (n1), r1/4
  spheroids (n4),and the range of profile shapes
  between them.

53
Morphology and Bulge/Disk Decomposition (by Chen
Zhu)

• Exemple of a galaxy with a bulge detected in the
  HST z-band image but not in the HST V-band image.

54
Morphology and Bulge/Disk Decomposition (by Chen
Zhu)

• In the GOODS field, 70 objects in the GOODS
  survey can be fitted with an exponential disk or
  present a minor merging event.
• In the GEMS (larger than GOODS field but
  shallower), more than 50 can be fitted with an
  exponential disk.
• From the sample that can be fitted with two
  components (bulge disk), the Sersic index of
  the bulge is smaller than for local galaxies.

55
Morphology of galaxies at z1 in the litterature

• Morphology still very debated
• De Mello et al. (2006) at z 1.5 all major
  morphological types with compact and peculiar
  more abundant at z gt 0.7
• Lotz et al. (2006) found no difference between
  the morphology of Uv-selected galaxies at z1.5
  and z4
• Ravindranath et al. (2006) studied LBGs at 1.5 lt
  z lt 5 40 have exponential light profiles
  similar to disks.
• Dahlen et al. (2007) found that the fraction of
  bulges decreases with the redshift.

56
Spectral Energy Distributions (RLBGs)
57
Abstract
20 RLBGs
80 BLBGs
LBG z 1 UVIR SFR
LBGs _at_ z 1
z 1 UV Lum. Density
All galaxies _at_ z 1
z 1 IR SF Density
Burgarella et al. (in press)
58
Evolution of Ldust / LFUV with redshift (Takeuchi
et al. 2007)
59
Evolution of Ldust / LFUV with redshift (Takeuchi
et al. 2007)
60
(No Transcript)
61
Comparison of several methods to estimate SFRTOT
62
Conclusion Project(s)

• Understand the (total) star formation
• ? measure SFRTOT
• Better calibrations ?L? ? Ldust
• Better knowledge of Ldust / LFUV (z) for
  UV-selected and IR-selected samples
• Better mesurements in IR and in UV
• Get physical information (SEDs, optical
  spectroscopy 2D et IR), modellisations
• Statistical Methods (compraison of SED with IR,
  smart  stacking  intelligent ltgt information on
  the distribution of undetected sources)

63
Deux parties
Bayesian SED Fitting

• Inputs
• SFH (t)
• Metallicity Z?
• Extinction 0.

PEGASE 2
Outputs Dust-free Spectra

• Inputs
• E(B-V)
• Attenuation laws

GALUVA (GALEX UV Attenuation)

• Outputs
• 82800 attenuated models
• Log(Fdust/UV)
• b0, b7, b8 (birthrate param)
• Colors

64
Evolution de Ldust / LFUV pour des galaxies
sélectionnées en IR (LIRGs)
LIRGs _at_ z 0 LIRGs _at_ z 0.7
lt A(FUV) gt 3.33 0.08 mag at z0.7 and lt
A(FUV) gt 3.810.13 mag at z0
Buat et al. (2007)
65
Lyman Break Galaxies
LBG
An introduction to
66
Attempt 1 estimate Ldust from UV

• Although a correlation might exists (Meurer et
  al. 99), the dispersion can be very large for
  normal galaxies (Bell 2002, Buat et al. 2005),
  for LIRGs/ULIRGs (Goldader et al. 2002).
• What about LBGs ?

67
Estimating SFRTOT from UV IR
68
IRX-? for RLBGs compared to Meurer et al.
(1999) and Kong et al. (2004)
69
IRX-? at 1.5 z lt 2

• Large luminosity galaxies are located above
  Meurer et al. (1999) law but LIR estimated from
  L5 - 8.5?m is likely to bear larger uncertainties
  than L12?m (i.e. 24?m at z1.5-2 and z1).

Reddy et al. (2006, astro-ph/0602596)
70
What about the famous IRX-? relation
?

• Meurer et al. suggested that the UV slope ? of
  the UV continuum could be used to estimate
• Ldust/LUV that is the UV dust attenuation
• The bolometric dust luminosity
• Total star formation rates of galaxies directly
  from UV
• The cosmic star formation history from UV only

71
Attempt 2 estimate Ldust from Spitzer/IRAC (3 -
8 ?m) only

• Huang et al. detected LBGs at z3 with Spitzer
  (only 4 with zspec) and much more at in the IRAC
  bands where SED is still dominated by stellar
  emission (uncertainty on Ldust ?)

Huang et al. (2005)
Chary Elbaz (2001)
72
Morphology of z 1 LBGsmainly disks and 75
are spirals
RLBG detected at 24 um BLBG undetected at 24 um
73
Discs observed in high z LBGs ?
Moorwood et al. (2000)

• No discs observed in high-z LBGs
• Simulations (e.g. Burgarella et al. 2001) suggest
  that detecting discs at z3 is extremely
  difficult
• ISAAC R 2000 spectroscopy
• Rotation curves detected consistent with discs

Pettini et al. (2001)
74
Comparison of z1 LBGs with zgt2 LBGs

• Huang et al. (05) 20 of z 3 LBGs is
  detected at 8 ?m and 24?m (ILLBGs)
• Burgarella et al. (06) 20 of z 1
  LBGs is detected at 24?m (RLBGs)
• ? similar percentage of dusty LBGs at all
  redshifts ?

75
Amount of dust attenuation

• About 20 of z1 LBGs have high dust attenuations
  (1 lt AFUV lt 5)
• Higher luminosity UV LBGs tend to have lower dust
  attenuations
• Average dust attenuation of 80 of z1 LBGs is
  very low (ltAFUVgt 0.5)
• Or, another parameter might affect the 24 um
  luminosity (metallicity ? e.g. Engelbracht et al.
  2005)

76
UV Luminosities of LBGs _at_ z1
UV Luminosities of LBGs _at_ z1
Z 1 LBGs
Z 1 LBGs
77
Avec densité de flux à 83 ?Jy
78
To estimate the amount of dust attenuation1) UV
Slope (f? ? ??) ? UV Dust Attenuation 2) FIR/UV
flux ratio

• UV slope OK for IUE (Meurer et al. 1999)
• ULIRGs (Goldader et al. 2002) and normal galaxies
  (Bell 2002) ? Problem ??
• Latter point confirmed Buat et al. 2005, Seibert
  et al. 2005, Burgarella et al. 2005)

• Kinney et al. (1993)
• Calzetti et al. (1994)

UV range
attenuation -
? (?m)
0.2
0.4
0.6
0.8
79
Why do we need the FIR for SED
fittings ?