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 H 2 NeII et al. H.Spoon, V. Charmandaris, L. Armus et al.

P. Morris

[NeV] [OIV] J. Bernard-Salas

IRS Goes Faint: CFRS σ ~ 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 : 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

The Optical Core of SBS HST optical image ~ 6 Super Star Clusters which produce the majority of the optical flux with 17 to 19 V mag /ascsec 2 The integrated IR flux is ~3x the optical output of the SSCs. The remainder of the IR “must” be supplied by buried SSC’s. Is there a population of IR only BCD’s? SIRTF will find out! Thuan et al. 1997

SBS : Selected Properties (pre Spitzer) z = ; D = 57 Mpc*; 280 pc / arcsec L ~ 1.2x10 9 L o L Optical ~ 3x10 8 L o & L MIR ~ 9x10 8 L o Z = Z o /41 from optical HII regions # Age ~ 5x10 6 yr M d /M o ~ 1X10 5 M * /M o ~ 1X10 7 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 Z o /50 Searle & Sargent 1972

SBS Red peak-up image. F = 71 +/- 11 mJy 18.5 to 26.0 microns 48 sec. exposure. Image is identical to that of a point source. 30”

IRS Spectra of SBS & NGC7714 Red Peak-up Gemini PAH [NeII] A(9.7 μ m) ~ 0.5

Continuum Spectrum

Estimating the FIR flux from the 1.4 GHz non-thermal radio flux. From the 1.4Ghz non- thermal we derive the FIR flux of 38mJy, ~5 times less flux in the ISO models. The smaller FIR flux implies a much smaller cold dust mass by a factor of ~ 4. M dust ~ 2.5 x10 4 M o

Fit to ISO Data T BB = 70 &150 K

Fit to Spitzer Data T BB = 70 &150 K

Fine Structure Line Results: Similar to the most extreme ultra-compact HII regions Martin-Hernandez (2002)

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, 2.5x10 4 M o –(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: –M d ~ 1.5x10 3 M o an even smaller dust mass.

Mid-infrared Line Radiation An infrared fine structure line flux & H β (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 S 3+ and Ne 2+ Z(S 3+ ) ~ 0.02 Z o (S) & Z(Ne 2+ ) ~ 0.09 Z o (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 Dist. ~ 57Mpc SBS Cool Dust & HI Visible HII regions Z~Z o /41 SNe shell Buried HII & SSC 17 pc dia. Age ~ 5x10 6 yr ~ 1 kpc ~ 4 arcsec N

SBS Properties (with Spitzer) z = ; D = 57 Mpc; 278 pc / arcsec L ~ 1.2x10 9 L o 1.0x10 9 L o L Optical ~ 3x10 8 L o Z = Z o /41 from optical HII regions Hidden infrared HII regions may have higher metallicity. Age ~ 5x10 6 yr for SSC M d /M o ~ 1X10 5 ~ 2.5x10 4

High Resolution observations are planned for SBS : 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, vF v,is at 20 microns while the peak in the flux, F v, 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.