Early results from the IRS

Jim Houck and the IRS team - AAS Denver 6/1/04

IRS Status

• The hardware is working well:– The responsively is better than expected– The noise is the same as in the lab– Suffered a major solar proton event; 2.5 year dose in 2.5 days!

• The data in the archive have one known and one suspected problem. The first is being fixed, and the second should be fixed in a few weeks.

• The sensitivity is ~2x worse due to lingering, few percent, issues with the darks, flats, etc.

• The first 18 ULIRGs from Spitzer.

• Very complex spectra with intertwined variations.

• Featuring:• PAHs• Ices• HACs• Silicates• H2

• NeII et al.• •

H.Spoon, V. Charmandaris, L. Armus et al.

[NeV]

[OIV]

J. Bernard-Salas

IRS Goes Faint: CFRS 14.1157

1σ ~ 0.35 mJy in 2880 sec.

Blue Peak-up

S.Higdon et al. ApJS 2004

• L(IR)=8E13 L(sun)• z=1.1• Automated fitting with NGC1068 template

Mid-IR spectrum is clearly AGN-like

Blue Compact Dwarf SBS 0335-052:

a nearby laboratory for the early Universe

with V. Charmandaris, B. Brandl, B. Bernard-Salas, et al.

SBS = Second Byurakan Survey Markarian et al. 1983

SBS0335-052: Selected Properties (pre Spitzer)

• z = 0.0136; D = 57 Mpc*; 280 pc / arcsec• L ~ 1.2x109 Lo

• LOptical ~ 3x108 Lo & LMIR ~ 9x108 Lo

• Z = Zo/41 from optical HII regions#

• Age ~ 5x106 yr • Md/Mo ~ 1X105

• M*/Mo ~ 1X107 • Radio: (Hunt et al. 2004)

– Diameter 17 pc (optical dia. ~ 1kpc)– Fluxes from 1.4 to 22 GHz – Separates the thermal and nonthermal components

* WMAP Cosmology # I Zw18 holds the record at Zo/50 Searle & Sargent 1972

SBS0335-052• Red peak-up image.F = 71 +/- 11 mJy18.5 to 26.0 microns48 sec. exposure.

• Image is identical tothat of a point source.

30”

IRS Spectra of SBS0335-052 & NGC7714

Red Peak-up

GeminiPAH

[NeII]

A(9.7μm) ~ 0.5

Implications for the Dust Mass

• ISO & IRS fit by two component model, 150 & 64K in both cases

• The cool dust component:– Contributes ~4 time less flux in the Spitzer case

– Therefore ~4 times less mass is needed, 2.5x104 Mo

– (The luminosity is dominated by the warm dust component and only changes at the 20% level.)

• However, the cool mass may also be inferred from the FIR flux, Hildebrand 1983:– Md ~ 1.5x103 Mo an even smaller dust mass.

Mid-infrared Line Radiation

• An infrared fine structure line flux & Hβ (derived from f-f radio flux) leads to an abundance:– The infrared flux is a weak function of electron

temperature and extinction– We detect only a single ionic line for S3+ and Ne2+

• Z(S3+) ~ 0.02 Zo(S) & Z(Ne2+) ~ 0.09 Zo(Ne)

– The SIV line is consistent with the expected emission from the optical regions.

– The NeIII is twice the flux predicted using the [NeIII] 3869A optical line.

HST: Thuan et al. 1997

Dist. ~ 57Mpc

SBS 0335-052

Cool Dust &HIVisible HII

regionsZ~Zo/41

SNe shell

Buried HII & SSC 17 pc dia.Age ~ 5x106 yr

~ 1 kpc ~ 4 arcsec

N

SBS0335-052 Properties (with Spitzer)

• z = 0.0136; D = 57 Mpc; 278 pc / arcsec

• L ~ 1.2x109 Lo 1.0x109 Lo

• LOptical ~ 3x108 Lo

• Z = Zo/41 from optical HII regions

• Hidden infrared HII regions may have higher metallicity.

• Age ~ 5x106 yr for SSC

• Md/Mo ~ 1X105 ~ 2.5x104

• High Resolution observations are planned for SBS 0335-052: SIII(2), SIV, NeII, NeIII(2), & NeV.

• ~20 well studied BCDs will be observed in Low res. and Hi res. if appropriate.

Conclusions & Future Plans • The peak in the luminosity, vFv,is at 20 microns while

the peak in the flux, Fv, is at 28 microns.

• The dust mass is smaller than previously thought• There is more [NeIII]15.55 micron flux than predicted

by the optical 3869 A line.