A New Detection of Extragalactic AME Eric J Murphy RadiotoFIR Spectrum of a Galaxy ν 08 ν 01 14 GHz 33 GHz ngVLA M51 Dumas et al 2010 20 cm14 GHz 36 cm83GHz H α AME over the last 20 years ID: 769723
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A New Detection of Extragalactic AME Eric J. Murphy
Radio-to-FIR Spectrum of a Galaxy ~ν -0.8 ~ν -0.1 1.4 GHz 33 GHz ngVLA M51 Dumas et al. 2010 20 cm/1.4 GHz 3.6 cm/8.3GHz H α
AME over the last 20 years First detected in 1996 as an excess CMB component Kogut et al. 1996; Leitch et al. 1997 Thought to arise from “spinning” dust Erickson 1957; Draine & Lazarian 1998Detected in a range of Galactic environmentsE.g., Finkbeiner et al. 2002; Dickinson et al. 2009First extragalactic detectionMurphy et al. 2010 Detected in 3 proto-planetary disksGreaves et al. 2018Status: Carrier and ISM conditions that drive AME still completely unknown 3 Perseus: Planck Collab. 2011 V892 Tau N6946 E4
Studying the Astrophysics of Star Formation in Nearby Galaxies Sample Derived From: SINGS/KINGFISH/GOALS 3.6 – 500 μ m imaging of 61+ nearby galaxies borne from SINGS sample IRS/PACS spec-mapping for 118 Nucs (56) + enucs (62)Additional ~68 LIRGs/ULIRGs from GOALS ( Barcos, Evans, Leroy, Linden, EJM) See Evans talk & Linden PosterSFRS: GBT/JVLA/ATCA/ALMA GBT: Ka-band for >~100 SINGS/KINGFISH SF regions (EJM+11,12) JVLA: S-, Ku-, and Ka-band for >~112 SINGS/KINGFISH SF regions (EJM+18a,b) + 88 local (U)LIRGs ALMA: for dense gas tracers (e.g., HCN, HNC, CS) for resolved SF Law work (EJM+15)The Star Formation in Radio Survey (SFRS)
The Pilot: NGC 6946 – The First Detection of Extragalactic AME PACS 100μm Sync. free-free Spinning Dust IR Ka-band (26-40GHz) CCB on GBT EJM+10 AMI (16.5 GHz) ( Scaife et al. 2010) CARMA (92 GHz) GISMO (150 GHz) See Hensley, EJM, & Staugun (2015) for latest modeling 5
A new detection of AME: NGC 4725 B ν (GHz) 3 15 22 33 44 Date Obs. 11/13 11/14 7/173/13,7/177/17 Radio Observations N=160 > 3σ EJM+18a EJM+18b 300pc 1.9 kpc 33 GHz Nucleus
A new detection – NGC 4725 B (optically invisible) Optical ( BVRI ) Mid-IR Spitzer EJM+18b 7
Similar 33GHz thermal fraction and AME luminosity as N6946E4 No obvious optical or non-thermal component Mid-IR counterpart (hot dust/small grains) Unlikely background given what (little) is known (Murphy & Chary 2018). Highly enshrouded, nascent star-forming region (<3 Myr). Implications for observed AME?Smallest grains not yet destroyed by SNe? A new detection – NGC 4725 B EJM+18b 8
9 New Extragalactic AME Candidates 29 AME Candidates ≈ 10 % of sources (N=291) r g > 250pc |α(15,33GHz) + 0.1|/σ > 3Potential Background Sources? 16 removed by eye from all SFRS detectionsUnlikely given n(S) (Murphy & Chary 2018)Proposal in to follow-up with VLA (15, 33, & 44 GHz)… ALMA (3mm) to follow. S. Linden et al. 2019, in prep.
10 Summary/Future Outlook 2/160 (~1%) sources have very large 33 GHz/24μm ratios & strong AME 30GHz (AME)/IR (dust) ~x2-3 larger in both N6946E4 and N4725B compared to MW values – most favorable extreme from strong AME ?Accepted ALMA proposal to look at 90GHz + CO emission from N4725BHST to do FUV spectroscopy to attenuation curves/grain size distributions & PAHsJWST to map 3.3/3.4 μm PAHs + nano-diamands from both sourceswritten and ready for June 2020!Real progress requires a next-generation radio instrument (e.g., ngVLA)Currently sensitivity starved in the radio to map large areas & PP disks! DS2020 WP being prepared
11 Prospects with the ngVLA A transformational step in studying star formation (and AME) in Galaxies H like images ( sens. /res.) w/out extinction, FG stars, or [NII] contamination VLA would need >800 hr to deliver same sensitivity EJM+ngVLA Science Book170 nJy/ bm1” beam 1.5 uJy/bm1” beam
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13 Comparison: N6946E4 & N4725B
Variations in Grain Distribution?Importance of MIR/FIR Spectral Maps Strength of 33 GHz AME/Excess Exposed to a near-average radiation field. Much less gas phase Fe + (IP~7.9eV) relative to Ne+ (IP~21.9eV) Fe locked up on grains that have not been processed by shocks?Abundance of small grains (a < 10 nm) present contributing to anomalous emission? A B Fe locked on grainsFe in gas phase