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XMM-Newton RGS Spectroscopy of the M31 Bulge. I. Evidence for a Past AGN Half a Million Years Ago
Zhang, Shuinai1,2; Wang, Q. Daniel3; Foster, Adam R.4; Sun, Wei1,2; Li, Zhiyuan5; Ji, Li1,2
2019-11-10
Source PublicationASTROPHYSICAL JOURNAL
ISSN0004-637X
Volume885Issue:2Pages:19
Corresponding AuthorZhang, Shuinai(snzhang@pmo.ac.cn)
AbstractExisting analysis based on spectra from the Reflection Grating Spectrometer (RGS) on board XMM-Newton already shows that the G-ratio of the O & xfffd;vii & xfffd;He? triplet in the inner bulge of M31 is too high to be consistent with a pure optically thin thermal plasma in collisional ionization equilibrium (CIE). Different processes that may affect properties of diffuse hot plasma were proposed, such as resonance scattering (RS) and charge exchange (CX) with cold gas. To determine which physical process(es) may be responsible for this inconsistency, we present a systematic spectroscopic analysis based on 0.8 Ms XMM-Newton/RGS data, together with complementary Chandra/ACIS-S images. The combination of these data enables us to reveal multiple non-CIE spectroscopic diagnostics, including but not limited to the large G-ratios of He? triplets (O & xfffd;vii, N & xfffd;vi, and Ne & xfffd;ix) and the high Lyman series line ratios (O & xfffd;viii Ly?/Ly? and Ly?/Ly?, and N & xfffd;vii Ly?/Ly?), which are not expected for a CIE plasma, and the high iron line ratios (Fe & xfffd;xviii 14.2 ?/Fe & xfffd;xvii 17 ? and Fe & xfffd;xvii 15 ?/17 ?), which suggest much higher temperatures than other line ratios, as well as their spatial variations. Neither CX nor RS explains all these spectroscopic diagnostics satisfactorily. Alternatively, we find that an active galactic nucleus (AGN) relic scenario provides a plausible explanation for virtually all the signatures. We estimate that an AGN was present at the center of M31 about half a million years ago and that the initial ionization parameter ? of the relic plasma is in the range of 3?4.
Keywordgalaxies: individual (M31) galaxies: ISM X-rays: galaxies
DOI10.3847/1538-4357/ab4a0f
WOS KeywordX-RAY-EMISSION ; HOT GAS ; CLUSTERS ; VOORWERP
Indexed BySCI
Language英语
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000499847200001
PublisherIOP PUBLISHING LTD
Citation statistics
Document Type期刊论文
Identifierhttp://libir.pmo.ac.cn/handle/332002/35102
Collection中国科学院紫金山天文台
Corresponding AuthorZhang, Shuinai
Affiliation1.Chinese Acad Sci, Purple Mt Observ, Beijing, Peoples R China
2.Chinese Acad Sci, Key Lab Dark Matter & Space Astron, Beijing, Peoples R China
3.UMASS, Dept Astron, Amherst, MA USA
4.Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA
5.Nanjing Univ, Sch Astron & Space Sci, Nanjing, Jiangsu, Peoples R China
Recommended Citation
GB/T 7714
Zhang, Shuinai,Wang, Q. Daniel,Foster, Adam R.,et al. XMM-Newton RGS Spectroscopy of the M31 Bulge. I. Evidence for a Past AGN Half a Million Years Ago[J]. ASTROPHYSICAL JOURNAL,2019,885(2):19.
APA Zhang, Shuinai,Wang, Q. Daniel,Foster, Adam R.,Sun, Wei,Li, Zhiyuan,&Ji, Li.(2019).XMM-Newton RGS Spectroscopy of the M31 Bulge. I. Evidence for a Past AGN Half a Million Years Ago.ASTROPHYSICAL JOURNAL,885(2),19.
MLA Zhang, Shuinai,et al."XMM-Newton RGS Spectroscopy of the M31 Bulge. I. Evidence for a Past AGN Half a Million Years Ago".ASTROPHYSICAL JOURNAL 885.2(2019):19.
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