NOAO >   Observing Info >   Approved Programs >   2019A-0121

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Program Information for 2019A-0121


PI: Aaron Watkins, University of Oulu, aaron.watkins@oulu.fi
Address: Astronomy Department, Penttikaiterankatu 1, Oulu 90014 Finland

CoI: Matthew A Bershady, U. of Wisconsin, Madison
CoI: Chris Mihos, Case Western Reserve U.
CoI: Paul Harding, Case Western Reserve U.
CoI: Sabyasachi Chattopadhyay, U. of Wisconsin, Madison

Title: Circumgalactic ionized gas around the Whirlpool: shock heated outflow or AGN-photoionized ejecta?

Abstract: We propose follow-up Sparsepak spectroscopy of a faint, extended ($sim 3^{prime}times10^{prime}$) cloud of diffuse ionized gas we recently discovered north of the famous interacting pair M51. Using both deep narrow-band imaging and red wavelength Sparsepak spectroscopy, we have firmly established the cloud's association with the M51 system (v$_{rm hel} sim$640 km s$^{-1}$), and measured line ratios ([OI]/H$alpha$, [NII]/H$alpha$, and [SII]/H$alpha$) suggesting a hard ionization source, such as AGN feedback. Confirmation would make this cloud the nearest example of an AGN ionization echo, akin to Hanny's Voorwerp near IC 2497. However, absent the [OIII] $lambda$5007/H$beta$ ratio, we cannot firmly constrain the hardness of the ionizing source, hence blue wavelength follow-up observations are necessary to fully understand the physical nature of this cloud. Most intriguingly, a non-detection of the cloud in our deep broadband imaging suggests an unusually low [OIII]/H$alpha$ ratio, possible if the cloud is at an early stage of recombination; if this is confirmed, this cloud may instead be an example of an extremely rare phenomenon known as a ``fossil nebula''.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2019A):  WIYN/SPSPK -- 4.5n on Jun 28 - Jul 06 2019


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2019A-0121

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