constraints on a universal imf 1 from the entire stellar population 2,3

Ivan Baldry, Constraints on an IMF from luminosity densities

Constraints on a Universal IMF1 from the Entire Stellar Population2,3

Ivan Baldry Johns Hopkins UniversityJohns Hopkins University

working with Karl Glazebrook working with Karl Glazebrook

22UV to IR galaxy luminosity densities (e.g. SDSS, FOCA, UV to IR galaxy luminosity densities (e.g. SDSS, FOCA, 2MASS, 2dFGRS and IRAS data) - “the Cosmic Spectrum”.2MASS, 2dFGRS and IRAS data) - “the Cosmic Spectrum”.

11Assuming a universal IMF and constraining the upper-mass Assuming a universal IMF and constraining the upper-mass IMF slope (M >~ 1 solar mass).IMF slope (M >~ 1 solar mass).

33Based on Baldry & Glazebrook, 2003, in ApJ, Vol. 593 Based on Baldry & Glazebrook, 2003, in ApJ, Vol. 593


Integrated Stellar PopulationsIntegrated Stellar Populations Extragalactic astronomers Extragalactic astronomers fit population synthesis modelsfit population synthesis models

to to colors or spectra of galaxiescolors or spectra of galaxies to gain insights into star to gain insights into star formation history, dust content, etc.formation history, dust content, etc.

Usually a stellar initial mass function (IMF) is assumed Usually a stellar initial mass function (IMF) is assumed because of the because of the age-IMF degeneracyage-IMF degeneracy..

This age-IMF degeneracy can be broken for the Universe as This age-IMF degeneracy can be broken for the Universe as a whole (assuming the Copernican principle):a whole (assuming the Copernican principle): Age = 13.70.2 Gyr (Spergel et al. 2003); Meas. of cosmic star formation history (Madau et al. 1996, `98); Meas. of the local “cosmic spectrum” (Baldry et al. 2002).


Overview of FittingOverview of Fitting Stellar initial mass function (IMF)Stellar initial mass function (IMF) Cosmic star formation history (SFR tracers 0 < z < ~5)Cosmic star formation history (SFR tracers 0 < z < ~5) Chemical evolutionChemical evolution Dust attenuationDust attenuation Population synthesis modelsPopulation synthesis models DATA – luminosity densities (0 < z < 0.2):DATA – luminosity densities (0 < z < 0.2):

FOCA (balloon), 0.2 microns (Sullivan et al. 2000); SDSS ugriz, 0.3-1 microns (Blanton et al. 2003); 2MASS, 2 microns, with z (Cole et al., Kochanek et al. 2001); H-alpha, attenuation-corrected (Gallego et al. 1995 and others); IRAS FIR (Saunders et al. 1990) converted to total dust emission.


Stellar IMF ParameterizationStellar IMF Parameterization

m–0.5 for 0.1 < m < 0.5 m– for 0.5 < m < 120nlog m is Salpeter slopeis Salpeter slope

Note unusual y-axis Note unusual y-axis scaling: mass fractionscaling: mass fraction


Cosmic Star Formation HistoryCosmic Star Formation History

SFR SFR (1+z)for zz<1 (0.5 < <1 (0.5 < < 4.0 allowed) and,< 4.0 allowed) and,SFR SFR (1+z) for 1 for 1<z<z<5 (SFR = 0 for z>5; meet at z=1).<5 (SFR = 0 for z>5; meet at z=1).

““Madau plot” Madau plot” versus timeversus time

REDSHIFTREDSHIFT

Various measurements, Various measurements, e.g, Lilly et al. 1996, e.g, Lilly et al. 1996, Madau et al. 1996/98, Madau et al. 1996/98, Cowie et al. 1999, Cowie et al. 1999, Steidel et al. 1999, Steidel et al. 1999, Lanzetta et al. 2002, + Lanzetta et al. 2002, + more.more.


Cosmic Chemical EvolutionCosmic Chemical Evolution

Compare ‘closed box’ with ‘constant metallicity’ approximations. Compare ‘closed box’ with ‘constant metallicity’ approximations. Allow average Z from about 0.5 ZAllow average Z from about 0.5 Zsolarsolar to 2 Z to 2 Zsolarsolar..

The cosmic stellar-mass The cosmic stellar-mass weighted metallicity is weighted metallicity is approx. solar (cf. our approx. solar (cf. our neighborhood in the neighborhood in the Milky Way).Milky Way).


Cosmic Dust Attenuation LawCosmic Dust Attenuation Law

Compilation from Compilation from Calzetti (2001).Calzetti (2001).

Estimated dust attenuation allowing for different contributions from late- and early-type galaxies as a function of wavelength. About 90% of the luminosity density is derived from late type galaxies at 0.2 microns and about 50% at visible to near-IR wavelengths.

Power-law with exponent ~ Power-law with exponent ~ ––0.80.8

Inclination-averaged Inclination-averaged attenuations.attenuations.


Population SynthesisPopulation Synthesis PEGASE.2 (Fioc & Rocca-Volmerange 1997, 1999):PEGASE.2 (Fioc & Rocca-Volmerange 1997, 1999):

Covers UV to IR; Includes stellar and nebular (continuum and line emission); Can specify arbitrary power law IMFs and SFH.

Evolutionary tracks from Padova group.Evolutionary tracks from Padova group. Theoretical spectra from Clegg & Middlemass (1987) Theoretical spectra from Clegg & Middlemass (1987)

and Lejeune et al. (1997) (derived from Kurucz models, and Lejeune et al. (1997) (derived from Kurucz models, NextGen and Fluks catalogues).NextGen and Fluks catalogues).

From the output spectra, determine:From the output spectra, determine: Colors through FOCA, SDSS and 2MASS filters; Total dust emission for various dust power laws; H-alpha luminosity (reprocessed Lyman continuum emission).


Data SummaryData Summary

BandBand mm

FWHMFWHM quantityquantity log(log(q q // h h W Mpc W Mpc-3-3)) References, notesReferences, notes

FOCA 2000FOCA 2000 0.200.20 0.020.02 ff 34.35 34.35 0.12 0.12 Sullivan et al. 2000Sullivan et al. 2000

SDSS SDSS 0.10.1uu 0.320.32 0.050.05 ff 34.25 34.25 0.08 0.08 Blanton et al. 2003Blanton et al. 2003

SDSS SDSS 0.10.1gg 0.420.42 0.110.11 ff 34.56 34.56 0.04 0.04 Blanton et al. 2003Blanton et al. 2003

SDSS SDSS 0.10.1rr 0.560.56 0.100.10 ff 34.73 34.73 0.04 0.04 Blanton et al. 2003Blanton et al. 2003

SDSS SDSS 0.10.1ii 0.680.68 0.110.11 ff 34.78 34.78 0.04 0.04 Blanton et al. 2003Blanton et al. 2003

SDSS SDSS 0.10.1zz 0.810.81 0.090.09 ff 34.83 34.83 0.04 0.04 Blanton et al. 2003Blanton et al. 2003

2MASS K2MASS Kss 2.162.16 0.280.28 ff 34.53 34.53 0.12 0.12 Average: Cole et al., Kochanek et al.Average: Cole et al., Kochanek et al.

HH 0.65630.6563 (line)(line) (bolo.)(bolo.) 32.63 32.63 0.20 0.20 Attenuation-corrected, Attenuation-corrected, averageaverage

TIRTIR 3–11003–1100 (broad)(broad) (bolo.)(bolo.) 34.70 34.70 0.15 0.15 ScaledScaled from FIR of Saunders et al. from FIR of Saunders et al.

Local Luminosity Density Measurements from Various Surveys (0<z<0.2)


Effect of Various ParametersEffect of Various ParametersA

B M

agni

tude

s (A

B M

agni

tude

s (

log

flo

g f

Wavelength (0.15-2.5 microns)Wavelength (0.15-2.5 microns)

Normalized at Normalized at 0.56 microns.0.56 microns.

DATADATA

FOCA, Sullivan FOCA, Sullivan et al. 2000et al. 2000

SDSS, Blanton SDSS, Blanton et al. 2003et al. 2003

2MASS, Cole et 2MASS, Cole et al. 2001, al. 2001, Kochanek et al.Kochanek et al.

Hawaii, Huang Hawaii, Huang et al. 2003et al. 2003


ResultsResultsAssuming: Assuming: constant SFR from z = 1 to 5constant SFR from z = 1 to 5, average metallicity = solar., average metallicity = solar.

Red contours for Red contours for constant Zconstant Z

Blue contours for Blue contours for closed box approx.closed box approx.

22=(=(11, 2.3, , 2.3, 6.26.2, 11.2), 11.2)

reds

hift

< 1

star

form

atio

n po

wer

law

reds

hift

< 1

star

form

atio

n po

wer

law

Fitting to 0.20, 0.32, 0.42, 0.56, 0.68, 0.81, 2.2 + HFitting to 0.20, 0.32, 0.42, 0.56, 0.68, 0.81, 2.2 + H + dust emission. + dust emission.

(Salpeter = 1.35)(Salpeter = 1.35)


Results continuedResults continuedAssuming: Assuming: high z>1 SFR high z>1 SFR (1+z)(1+z)22, average metallicity = solar., average metallicity = solar.

Red contours for Red contours for constant Zconstant Z

Blue contours for Blue contours for closed box approx.closed box approx.

22=(=(11, 2.3, , 2.3, 6.26.2, 11.8), 11.8)

reds

hift

< 1

star

form

atio

n po

wer

law

reds

hift

< 1

star

form

atio

n po

wer

law

Fitting to 0.2-0.8, 2.2 + HFitting to 0.2-0.8, 2.2 + H + total dust emission. + total dust emission.

(Salpeter = 1.35)(Salpeter = 1.35)


Results continuedResults continued 1.11.1±0.2±0.2 marginalized over dust, SFH, 0.5<Z/Z marginalized over dust, SFH, 0.5<Z/Zsolarsolar<2.<2. Scalo IMF is inconsistent with data and models (cf. Scalo IMF is inconsistent with data and models (cf.

Madau, Pozzetti & Dickinson 1998 and Kennicutt, Madau, Pozzetti & Dickinson 1998 and Kennicutt, Tamblyn & Congdon 1994 [incl. HTamblyn & Congdon 1994 [incl. H EWs]). EWs]).

Stellar mass density of the Universe is in the range Stellar mass density of the Universe is in the range 0.15% to 0.28% (0.15% to 0.28% (0.12% to 0.35%0.12% to 0.35% with low-mass IMF with low-mass IMF uncertainty, or uncertainty, or 3% to 8%3% to 8% of baryon density). of baryon density).

Stellar bolometric emission is (1.7-2.4) x 10Stellar bolometric emission is (1.7-2.4) x 103535 W Mpc W Mpc-3-3 and dust emission is (0.4-1.0) x 10and dust emission is (0.4-1.0) x 103535, which implies a , which implies a modest modest effective average attenuationeffective average attenuation in the ultraviolet in the ultraviolet of of AA20002000 < ~60% < ~60% (< ~1 mag). (< ~1 mag).

CAVEAT – results rely on accuracy of population CAVEAT – results rely on accuracy of population synthesis…synthesis…


Local Luminosity DensitiesLocal Luminosity Densities

Data and best-fit model spectrum: the stellar and the HII region gas emission (Fioc & Rocca-Volmerange) and; the dust emission (Dale & Helou). AGN contribution not shown.

bolo

met

ric l u

mi n

o si ty

per

log

bolo

met

ric l u

mi n

o si ty

per

log

bin

bi n


Future and Current SurveysFuture and Current Surveys Local imaging surveys (z~0.1):Local imaging surveys (z~0.1):

(SDSS has set the bench mark, >105 galaxies with redshifts and ugriz photometry, >103 deg2) – optical;

GALEX all-sky survey – ultraviolet; VISTA – near-infrared (also 2MASS with 6dFGS

redshifts); ASTRO-F – mid- to far-infrared.

Deeper imaging surveys:Deeper imaging surveys: GALEX deep surveys – ultraviolet; HST – ACS, NICMOS – optical, near-IR; SIRTF – mid- to far-infrared.


……

Extra slides follow.Extra slides follow.


Cosmic Star Formation HistoryCosmic Star Formation History Meas. of comoving star-formation rate density Meas. of comoving star-formation rate density

(M(MOO/yr/Mpc/yr/Mpc33) as a function of redshift (or time).) as a function of redshift (or time).

Determine SFR per Determine SFR per comoving volume:comoving volume:

LLuvuv, L, LFIRFIR, L, L700Mhz700Mhz

LLHH, L, LHH, L, L[OII][OII]

Number of Number of massive stars massive stars formed / unit timeformed / unit time

(modulo dust, (modulo dust, SB, etc… SB, etc… corrections)corrections)

CSFH analysis removes CSFH analysis removes uncertainties associated uncertainties associated with dynamical history, i.e. with dynamical history, i.e. consider the Universe to be consider the Universe to be a single average galaxy.a single average galaxy.


Madau, Pozetti & Dickinson 1998Madau, Pozetti & Dickinson 1998

2.2 2.2 mm

1.0 1.0 mm

.44 .44 mm

.28 .28 mm

.15 .15 mm

Fig 3: Salpeter IMF; Fig 3: Salpeter IMF; SMC-type dust in a SMC-type dust in a foreground screen; foreground screen; E(BE(B––V)=0.1.V)=0.1.


Madau, Pozetti & Dickinson 1998Madau, Pozetti & Dickinson 1998

Scalo IMF, no dustScalo IMF, no dust Salpeter IMF, E(BSalpeter IMF, E(B––V) V) = 0.011(1+z)= 0.011(1+z)2.22.2

2.2 2.2 mm

1.0 1.0 mm

.44 .44 mm

.28 .28 mm

.15 .15 mm


Table of IMF ComparisonsTable of IMF Comparisons

constraints on a universal imf 1 from the entire stellar population 2,3

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