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The Slit-Less Spectroscopic Survey of Galaxies (SPICY) with AKARI/IRC – perspective to SPICA

This paper discusses the SPICY survey, a slit-less spectroscopic survey of galaxies conducted using the AKARI/IRC instrument. The aim is to study the mid-infrared spectra of galaxies, particularly the polycyclic aromatic hydrocarbon (PAH) features, which serve as indicators of star formation and active galactic nuclei (AGN) activity.

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The Slit-Less Spectroscopic Survey of Galaxies (SPICY) with AKARI/IRC – perspective to SPICA

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  1. The Slit-Less Spectroscopic Survey of Galaxies (SPICY) withAKARI/IRC – perspective to SPICA T. Wada, Y. Ohyama, H. Matsuhara, M. Malkan, T. Goto, E. Egami, J.H. Kim, C. Pearson, H. Inami, D. Burgarella, T. Miyaji, T. Nakagawa, et al. Y. Ohyama, T. Wada, H. Matsuhara, et al. 2018 A&A 618, A101 (2018) SPICA 2019

  2. contents • Mid-infraredspectrum of galaxies • AKARI NEP extragalactic survey • AKARI Spectroscopic Survey of Galaxies • PAH galaxies • FIR-PAH relation • Toward SPICA SPICA 2019

  3. Mid-infrared spectra of galaxies (Sloan et al. 2003)

  4. Mid-infrared spectra of galaxies Silicate (Sloan et al. 2003)

  5. Mid-infrared spectra of galaxies PAHs (Sloan et al. 2003)

  6. Why PAH? • “spectroscopic” redshift • Star-formation/AGN indicator • More luminous than the other diagnostic lines • High-z or low-L • Broad feature matches low-R spectroscopy • Wide FoV can be obtained with same # of detector pixels • Higher survey speed • Follow-up spectroscopy is necessary for accurate measurement of physical conditions, but a lot of information can be obtained by PAH.

  7. Redshift indicator • “PAH bands” are not “unidentified” infrared bands • Realistic emission mechanism, C-C C-H stretching and bending, is proposed. (e.g. Allamandola et al. 1989) the polycyclic aromatic hydrocarbon (PAH) lines (Draine 2003)

  8. Star-formation/AGN indicator • A tracer for star-forming activity • PAH absorb UV light from young stars and re-emits its energy in MIR • A (negative) tracer for AGN activity • PAH molecules are destroyed by X-ray light from the AGN Imanishi et al. reveals energy source of ULIRGs by 3.3um PAH features (Imanishi et al. 2010, ApJ 721, 1233) SPICA 2019

  9. Starburst/AGN PAH(7.7)/continuum Genzel et al. 1998, ApJ 498, 570

  10. What AKARI brings us? • AKARI NEP DEEP/WIDE survey • 2-24um, 9 contiguous bands, no “IRAC/MIPS gap” • DEEP 0.4 sq deg. 120uJy at 15um (Wada et al. 2008) • WIDE 6 sq deg. 150uJy at 15um (Lee et al. 2009) • Slit-less spectroscoPIC survey of galaxY (SPICY) • 2.5-24um (15-18um is lost) • Spectral resolution of R=30-50 • 10 of 10’x10’ fields in NEP DEEP/WIDE area • 100 minutes per field, 17 hours in total. • Flux limited complete sample, S(9um) > 0.3mJy SPICA 2019

  11. AKARI The AKARI NEP Survey • Deep : 0.5 deg2 (259 pointing) Wada et al. 2008, Murata et al. 2013 • Wide : 5.4 deg2 (446 pointing) Lee et al. 2009, Kim et al. 2012 1 deg NEP-Wide NEP-Deep CFHT/Mega-prime cam GAP Imaging with nine IRC wavebands (N2, N3, N4, S7, S9W, S11, L15, L18W, L24)

  12. Multi-wavelengthSurvey Data toward NEP Japan (ISAS, TUS, Nagoya U., KwanseiGakuin U., NAOJ ..), Korea（KASI,SNU）, Taiwan (NTHU, ASIAA), US (UCLA), Mexico (UNAM), UK (RAL, OU), France (LAM), etc. X-ray Opt-NIR FIR-Submm NIR-MIR-FIR radio FUV NUV AKARI

  13. SG1 S11 S7 CAL SG2 S9W Y,λ X Y X InfraRed Camera (IRC) as a spectrograph • For NIR-MIR imaging & spectroscopy • Comprising of three channels (NIR/MIR-S/MIR-L) • With selectable filters/grisms or prism • Uniqueness/Advantage over the Spitzer: • Larger FOV/Slit-less spectroscopy • Wide and continuous spectral coverage over entire NIR-MIR (2~25mm) The ``Slit-less’’ Concept direct image spectral image 10 arcmin 10 arcmin Selectable filter wheel SPICA 2019

  14. The SPICY dataset Blind MIR spectroscopic survey 5 – 13 mm spectra of all object > 0.3mJy at 9um (Ohyama et al. 2018) NEP-Deep Foreground stars Nearby PAH galaxies The NEP Nearby AGN with Silicate absorption

  15. Ohyama et al. 2018 • In total N=171 galaxies • SPICYPAH galaxies: N=48 • PAH-undetected galaxies: N=112 • Photometric AGN candidates: N=11 SPICA 2019

  16. Identification of PAH • Fit by 6.2, 7.7, 8.6, and 11.3um PAH feature and baseline • Free-parameters are • Redshift • Each PAH peak and sigma (Gaussian) • 48 galaxies are successfully identified as SPICY PAH galaxies. SPICA 2019

  17. Accuracy in Redshift determination • Red redshift obtained by PAH fitting is consistent with that by optical spectroscopy. (Shim et al. 2013) • Simple fitting with low-resolution spectroscopy of PAH gives us a good redshift measurement. SPICA 2019

  18. property of SPICY PAH gals maximum starburst SPICY Spitzer/IRS Spitzer/IRS galaxies Weedman & Houck 2008 SPICA 2019

  19. property of SPICY PAH gals SPICY Volume limit Flux limit SPICA 2019

  20. Limitation of SPICY PAH sample • We used 5-12um data only. Redshift range is z<0.5 because 7.7 um feature goes out of range. • PAH is prominent, but continuum is hard to detect with this sensitivity. SPICA 2019

  21. Assistance of photometric data • SPICY detects PAH emission from distant galaxies. • Now, spectroscopic redshift and PAH luminosity are known for these SPICY PAH gals • But no stellar continuum is obtained because of limited sensitivity and spectral coverage. • We use NEP WIDE photometric data in order to obtain full NIR/MIR coverage, especially, stellar continuum component (rest frame 3.5um) SPICA 2019

  22. Stellar continuum is always stellar continuum SEDs of 48 SPICY PAH galaxies (rest-frame) 3.5um SPICA 2019

  23. PAH enhanced population Main sequence PAH-enhanced population • Gray shaded area: main sequence for z~0 blue SDSS galaxies (Elbaz+07) SPICA 2019

  24. FIR-PAH relation SPICA 2019

  25. The Herschel-PACS North Ecliptic Pole SurveyPearsonetal.2019

  26. 9um, 100um, 160um, OPT images of SPICY PAH galaxies SPICA 2019

  27. 9um, 100um, 160um, OPT images of SPICY PAH galaxies SPICA 2019

  28. FIR-PAH relation Log LIR/Lsun= 0.25 + Log 𝜐L𝜐7.7μm/Lsun SPICA 2019

  29. SPICY summary • The world first MIR unbiased spectroscopic survey has been conducted (>0.3mJy at 9um). • 48 PAH galaxies are detected z=0.1~0.5 with LIR=109.5-11.5Lsun • Good correlation between spectroscopic redshift of OPT and PAH; PAH is a good redshift indicator. • We found PAH-enhanced galaxies at high-z(z>0.35) or high-L PAH, which has higher PAH/stellar mass ratio rather than the main sequence galaxies. • Good correlation between PAH and FIR luminosity: PAH is cost-effective indicator of star-formation. SPICA 2019

  30. Toward SPICA • D=68cm => 2.5m diffraction limited image • Sharp beam with larger collecting area • Low luminosity galaxies • High-z • Less source confusion • Longer and wider spectral coverage • 2-24um (AKARI/IRC)=> 17-36um (SMI/LR) • Trace the PAH(11.3-6.2) at z=0.5-4, where the cosmic star-formation rate peaks! • 12-230um contiguous spectrum, MIR-FIR spectrum since ISO. SPICA 2019

  31. SPICA/SMI/MR+SAFARI • 17-230um R=300-1000 spectrometer • A few 10-20W/m2 level line sensitivity with 1 hour 5 sigma • z=3 ULIRGs can be followed up by dust extinction free IR diagnostic lines! SPICA 2019

  32. SPICA/SMI/LR+CAM • 17-36um R=100 spectrometer with 34um camera • Wide field of view (10’x3.7”x4 slit spec. and 10’x12’ img.) • 30uJy level sensitivity with 1 hour 5 sigma • z=3 ULIRGs can be detected in blind survey! SPICA 2019

  33. uJy level sensitivity probes ULIRGs at z=3 SPICA 2019

  34. Blind survey and follow-up 4.1. Overview Follow-up observations Targets observed by (18–230 mm, R=300–1000) AKARI, Subaru, Spitzer, Herschel, ALMA, JWST, Euclid, SKA, TMT, ATHENA, TESS, PLATO,,, SMI/MR・SAFARI • high-z galaxies, AGN outflow, • nearby dwarf galaxies,,, • Pointed spectroscopy • Spectral mapping of nearby • galaxies • Spectral mapping of Galactic • objects • proto-planetary disks, debris • disks, exo-planets,,, SMI/LR Unbiased spectroscopic survey (17–37 mm, R=50–100) + (34 mm R=5) • 10 deg2 blind survey (600 hrs) Better statistics (51,000 PAH galaxies 3,700 AGNs 13,000 MS stars) • 1 deg2 blind survey (500 hrs) Fainter objects (sub-L* galaxies, faint debris disks)

  35. 皮算用 SF/AGN Diagnostics by PAH and silicate AGN/starburst co-evolution AGN contribution For SF/AGN mixture ■ ■ z = 3 ■ ■ ■ ■ ■ ▲ ■ ■ ■ ▲ ■ ■ ▲ ■ ■ ▲ ■ ■ ▲ ■ ■ ■ ■ ▲ ■ ▲ ■ ■ ▲ ■ ■ ■ ▲ ■ ▲ ■ ▲ ■ ▲ ■ + ▲ ■ ■ ■ ■ ▲ ▲ ■ ■ ▲ ▲ ■ ▲ ■ 10x L* ■ All the 51,000 PAH galaxies3,700 AGNs ▲ ■ ■ ▲ ▲ ▲ z = 2 ▲ ▲ ▲ ■ ▲ ▲ ▲ ▲ ● 3x L* ■ ▲ ● ● L(AGN) ▲ ▲ ▲ ● with basic information z, L, AGN/SF ratio ▲ ● ▲ ▲ ▲ ● ● ▲ + ● ● ● ● ● ▲ + ● ● ● ▲ ● ● + z = 1 ● ● ● ● ● ● ● ● L* at z=1 ● ● ● + + + + ● ● ● ● ● + ● + + ● ● ● ● ● ● ● + Uniformly sampled > 1,000 galaxies ● ● ● ● + ● ● + + ● ● ● ● ● ● + + + + + ● + ● ● ● ● + ● ● + + + + + + + + z = 0.5 + + + + + + L(SF) Dust formation & growth Relation to metal enrichment For pure SF galaxies, Top-heavy IMF ? • [NIII]57/[OIII]52 • → metallicity • PAH/[OIII] • → (dust/gas)/(metallicity) • [NeIII]/[NeII] • → radiation temperature z = 2 Metallicity z = 1 [NeIII] / [NeII] ▲ ▲ + + ● ● ▲ ▲ ▲ + ▲ + z = 0.5 + ● ● + ● ● ▲ ● ▲ ▲ + ▲ + ▲ + ▲ ▲ + + ● ▲ + + ● ● ▲ ● + ▲ + ● ● ▲ + PAH / [OIII] + ● + ▲ ● ● ● ● metallicity

  36. summary • The world first MIR unbiased spectroscopic survey has been conducted (>0.3mJy at 9um). • 48 PAH galaxies are detected z=0.1~0.5 with LIR=109.5-11.5Lsun • Good correlation between spectroscopic redshift of OPT and PAH; PAH is a good redshift indicator. • We found PAH-enhanced galaxies at high-z(z>0.35) or high-L PAH, which has higher PAH/stellar mass ratio rather than the main sequence galaxies. • Good correlation between PAH and Herschel PACS FIR luminosity: PAH is cost-effective indicator of star-formation. • SPICA will probe these galaxies redshift at z=0.5-4, the most active era of galaxy evolution. SPICA 2019

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