Rudy Gilmore SISSA Santa Cruz Galaxies Conference UCSC August 10, - - PowerPoint PPT Presentation

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Rudy Gilmore SISSA Santa Cruz Galaxies Conference UCSC August 10, - - PowerPoint PPT Presentation

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Modeling of the Extragalactic Background Light Rudy Gilmore SISSA Santa Cruz Galaxies Conference UCSC August 10, 2011 Wednesday, August 10, 2011 Somerville et al. - ArXiv:1104.0669 (MNRAS submitted) Gilmore et al. - ArXiv:1104.0671 (MNRAS

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Modeling of the Extragalactic Background Light

Rudy Gilmore

SISSA Santa Cruz Galaxies Conference UCSC August 10, 2011

Wednesday, August 10, 2011

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Collaborators:

 Joel Primack - UCSC  Rachel Somerville - STScI  Alberto Domìnguez - UCSC and Inst Astro Andalusia

Somerville et al. - ArXiv:1104.0669 (MNRAS submitted) Gilmore et al. - ArXiv:1104.0671 (MNRAS submitted)

Outline

✓ Modeling the evolving extragalactic background light with semi-analytic methods ✓ The EBL and gamma-ray sources ✓ Comparison with other results and future work

Wednesday, August 10, 2011

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The Extra-Galactic Background Light (EBL) Photon population created by structure formation (stars+AGN+others?)

Determining the EBL from observations is difficult:

★ Direct photometry measurements must contend with difficult foreground subtraction and calibration issues! ★ Number counts available at many wavelengths, but degree of convergence often controversial, also fringe issues, source confusion.

Direct Starlight Thermal Dust Emiss. PAH

Fully understanding the creation and evolution of this photon population requires sophisticated modeling

Observationally-based models:

Kneiske et al. (2002; 2004); Finke et al. (2010); Younger & Hopkins (2011); Dominguez et al. (2011)

Backward evolution:

Stecker et al. (2006); Franceschini et al. (2008)

Forward evolution (semi-analytic) models:

Primack et al. (2005; 2008); Gilmore et al. (2009), this work

Wednesday, August 10, 2011

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EBL from observations:

  • Uses evolution galaxy number fraction across 25 spectral types seen in some 6000 AEGIS

galaxies, with normalization to K-band luminosity functions (Cirasuolo 2010)

5 sample templates: AGN and starburst-like spectral type fractions increase with redshift to z~1, while quiescent decrease.

  • AEGIS multiwavelength data covers several optical

and NIR bands, IR (IRAC and MIPS), and UV (GALEX)

  • High redshift (z > 1): 2 assumptions about

evolution of SED types were considered Dominguez et al., 2011

MNRAS 410, 2556 (ArXiv:1007.1459)

Wednesday, August 10, 2011

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EBL from our semi-analytic model

  • Treats co-evolution of AGN, black holes, and galaxies

in ΛCDM framework

  • Based on model of Somerville et al. (2008), including:
  • Galaxy formation based on hierarchical buildup of cold dark

matter halos.

  • Star formation in quiescent and burst (merger-triggered) modes,

with regulation by AGN feedback. Stellar emission spectrum from Bruzual & Charlot (2003).

  • Optical and UV starlight absorbed using (modified) dust model of

Charlot & Fall (2000), IR re-emission based on Spitzer templates

  • Model parameters set by well-determined local observables and

results from simulations of galaxy mergers

Our recent work:

➡ “CLCDM” model based on concordance (WMAP1) cosmology

(Primack, Gilmore, Somerville 2008)

  • Gilmore et al. 2009: Focused on high-z UV evolution, included QSO

component, comparison with IGM data

➡ This work based on new WMAP5/7 model with updated

cosmological parameters

Wednesday, August 10, 2011

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WMAP1 Model (Primack et

  • al. 2008)

WMAP5 (this work) Hopkins & Beacom 2006 best fit Dominguez et al. (2011)

(inferred from UV and IR light)

Star formation rate density across cosmic time

Wednesday, August 10, 2011

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Far-UV evolving luminosity functions

Dust Absorption of Starlight

  • Our results use dust absorption

model of Charlot & Fall 2000.

  • Our fiducial model includes an

additional `evolving dust’ factor to correct UV (right) luminosity functions.

  • Currently looking at effect of

increased resolution of small haloes (strongest effect in high-z UV output) solid: evolving dust dashed: no dust blue dashed: fixed dust

Wednesday, August 10, 2011

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Re-emission by Dust

  • Starlight absorbed by dust is re-emitted in

the IR (energy in = energy out)

  • Our older models have used templates

from Devriendt & Guiderdoni (1999), based

  • n IRAS
  • Our new WMAP5 model uses templates of

Rieke et al. (2009), based on Spitzer data.

  • Rieke templates predict lower emissivity

from 10 to 50 microns, esp for bright galaxies.

Wednesday, August 10, 2011

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FUV

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NUV

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u-band

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g-band

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r-band

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i-band

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z-band

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K-band 8 9 10 11 12 13

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Total IR

Local Luminosity Functions

solid: Fiducial dashed: no dust dotted: CLCDM

Log(Solar Lum.)

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2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6

Predicted luminosity density

Fiducial Fixed-dust Dominguez et al. (2011)

z = 0 data:

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The Local Background Flux

  • We predict a flux near the

level set by number counts at most wavelengths.

  • Below diffuse near-IR

background claims of DIRBE/ IRTS

  • Large uncertainty remains in

far-IR; conflicting results between methods

GALEX HST IRAC DIRBE (NIR) MIPS BLAST FIRAS Herschel ISO DIRBE (FIR)

Wednesday, August 10, 2011

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1000 1 10 100 1000 0.1 1 10 1000 1 10 100 1000 0.1 1 10

EBL Buildup

Rest Frame: Observed Frame:

Wednesday, August 10, 2011

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Gamma-ray attenuation

Gamma-ray optical depth vs energy at several redshifts

Cosmological “Attenuation Edge”

Contours of constant tau in redshift and observed energy Fiducial Fixed-dust Dominguez et al. (2011)

F u t u r e I A C T

  • b

s ?

Absorption of Gamma Rays by EBL

  • Gamma-ray attenuation via e+e- pair production provides a link between galaxy

history and high energy astrophysics.

  • This leads to softening and cutoff in gamma ray spectra of distant extragalactic

sources (blazars and GRBs), as well as gamma ray horizon.

Wednesday, August 10, 2011

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Our models with gamma-ray upper limits

Our models are within new low bounds set by blazar

  • bservation

(Γ ≤ -1.5 criterion) (Mazin & Raue 2007)

limits from 14 gamma-ray blazars

H 2356-309 and 1ES 1101-232 (z=0.165 and 0.186) (Aharonian 2006) 3C279 (z=0.536) (Albert 2008)

GR upper limits below some direct detection claims

DIRBE (NIR) IRTS Bernstein (2007) Dwek & Krennrich (2005)

Wednesday, August 10, 2011

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This work CLCDM Kneiske+04 ‘best fit’ Finke+10 Model ‘C’ Stecker+06 (Baseline and Fast Evolution) Dominguez+11 Franceschini+08

Comparison of redshift evolution in recent EBL models

Wednesday, August 10, 2011

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Conclusions

✦ Using semi-analytic techniques, we have created an updated model of background light from the UV to far-IR ✦ We match well with measured number counts, luminosity functions, and luminosity density ✦ General convergence between results from our SAM and very different modeling techniques (Franceschini 2008, Finke 2009, Dominguez 2011) out to z~1... ✦ ...However, large uncertainties remain in high-z evolution of UV flux, and overall normalization of IR peak. ✦ Our model is near the level of resolved light (number counts) over wide range of wavelengths. ✦ Agreement with limits from gamma-ray experiments. ✦ Low levels of background are good news for Fermi and next-gen ground-based

  • instruments. EBL does not significantly impede observations below 100 GeV at z < 1

Wednesday, August 10, 2011

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0.1 1 10 100 1000 0.1 1 10 100 1000 ACS b ACS i 15 20 25 30 0.1 1 10 100 1000 ACS z 15 20 25 30 K-band IRAC 3.6 IRAC 8.0 MIPS 24 MIPS 70 SPIRE 250 SCUBA 850

Galaxy number counts

Wednesday, August 10, 2011

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0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1 1 2 3 0.2 0.4 0.6 0.8 1

Data:

Lefloch (2009) (24 micron) Jauzac (2011) (70 and 160)

Wednesday, August 10, 2011

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Wednesday, August 10, 2011