Circumnuclear Dust in AP Librae and the source of its VHE emission

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dc.contributor.authorRoychowdhury, Agniva
dc.contributor.authorMeyer, Eileen T.
dc.contributor.authorGeorganopoulos, Markos
dc.contributor.authorBreiding, Peter
dc.contributor.authorPetropoulou, Maria
dc.date.accessioned2021-11-18T18:50:22Z
dc.date.available2021-11-18T18:50:22Z
dc.date.issued2021-10-28
dc.description.abstractThe broad high-energy spectral component in blazars is usually attributed to various inverse Compton scattering processes in the relativistic jet, but has not been clearly identified in most cases due to degeneracies in physical models. AP Librae, a low-synchrotron-peaking BL Lac object (LBL) detected in 2015 by H.E.S.S. at very high energies (VHE; > 0.5 TeV), has an extremely broad high-energy spectrum, covering ∼ 9 decades in energy. Standard synchrotron self-Compton models generally fail to reproduce the VHE emission, which has led to the suggestion that it might arise not from the blazar core, but on kiloparsec scales from inverse Compton scattering of cosmic microwave background (CMB) photons by a still-relativistic jet (IC/CMB). IC/CMB models for the TeV emission of AP Librae in prior works have implied a high level of infrared emission from the kpc-scale jet. With newly obtained Hubble Space Telescope imaging, we obtain a deep upper limit on the kpc-scale jet emission at 1.6 μm, well below the expected level. High-resolution ALMA imaging in bands 3-9 reveals a residual dust disk signature after core subtraction, with a clearly thermal spectrum, and an extent (∼500 pc) which matches with a non-jet residual emission seen after PSF subtraction in our 1.6 μm HST imaging. We find that the unusually broad GeV and VHE emission in AP Librae can be reproduced through the combined IC scattering of photons from the CMB and the dust disk, respectively, by electrons in both the blazar core and sub-kpc jet.en_US
dc.description.sponsorshipThis paper is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. This work was supported by the HST-GO grant 15175. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.01411.T, 2017.1.00568, 2017.1.00995, 2017.1.00258, 2017.1.01583, 2017.1.00963, 2017.A.00047, 2017.1.00239, 2013.1.00244, 2017.1.01555, 2017.A.00047, 2017.1.00337, 2017.1.00023, 2017.1.01555. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Incen_US
dc.description.urihttps://arxiv.org/abs/2110.12016en_US
dc.format.extent25 pagesen_US
dc.genrejournal articlesen_US
dc.genrepreprintsen_US
dc.identifierdoi:10.13016/m2e9tu-yikb
dc.identifier.urihttp://hdl.handle.net/11603/23386
dc.language.isoen_USen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Physics Department
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.en_US
dc.titleCircumnuclear Dust in AP Librae and the source of its VHE emissionen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0003-1101-8436en_US
dcterms.creatorhttps://orcid.org/0000-0002-7676-9962en_US
dcterms.creatorhttps://orcid.org/0000-0002-2040-8666en_US

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