Astronomy:3C 345

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Short description: Quasar in the Hercules constellation
3C 345
3C 345 Color cutout hst 05235 03 wfpc2 f814w f555w pc sci.jpg
Image of 3C 345 by the Hubble Space Telescope
Observation data (Epoch J2000)
ConstellationHercules
Right ascension 16h 42m 58.8s[1]
Declination+39° 48′ 37″[1]
Redshift0.5934 [1]
Distance5.497 Gly
TypeOpt.var.;HPQ, FSRQ
Apparent magnitude (V)16.6[1]
Notable featuressuperluminal jet
Other designations
4C +39.48, LEDA 084767[1]
See also: Quasar,List of quasars]]
Total intensity image of the inner region of 3C 345 at 1.6 GHz[2]

3C 345 is a blazar/flat spectrum radio quasar located in the constellation of Hercules. It is noted for hosting a superluminal jet[3] and its variability in almost all wave bands.

Characteristics

3C 345 has an active galactic nucleus that has been categorised as a blazar or as a flat spectrum radio quasar. The host galaxy of 3C 345 is an E3 elliptical galaxy without prominent peculiar characteristics.[4]

Superluminal jet

When observed in radio waves, 3C 345 features a compact region with a radio jet emanating from it for 3 arcseconds and ending at a hot spot.[3] The jet appears straight for 4 milliarcseconds (mas)[3] but then curves northwards. Hot spots are visible at the counterjet direction in radio images.[5] There is also a faint halo.[3] The jet has been found to emit X-rays, up until 0.2 arcseconds from a radio hot spot, which could be in reality a bend of the jet.[5]

The components of the jet have been found to move by about 0.25–0.42 mas, which at the distance of the jet represent apparent speeds that are 5 to 15 times faster than the speed of light.[6] The radio jet exhibits superluminal motion for 0.12 to 12 mas, with apparent speeds that accelerate from ~5c to ~15c within 0.3 mas. Within the jet lies a stationary feature ~0.1 mas (with corresponds to about 0.7 pc at the distance of 3C 345) from the core, which has also been found in other blazars.[6] The viewing angle between the jet axis and the line of sight is calculated to be about 5°.[6]

Variability

3C 345 has been known to fluctuate in brightness. For example, it brightened from magnitude 17.2 to 16.0 between 10 April 2018 and 8 May 2018 when observed in R band.[7] A bright GeV gamma-ray flare was observed by the Fermi Gamma-ray Space Telescope on 31 May 2017, as the flux increased by 40 times above average.[8] The flares in 2009 were observed simultaneously in γ-rays, X-rays and optical/UV, while there was a lag before they were observed in radiowaves.[9] A long term variability study indicates flares every 3.5 to 4 years, coinciding with the appearance of new features in the radio jets.[10]

It has been suggested that the source of the fluctuation is the presence of a binary supermassive black hole, with the two similar black holes with masses about 7.1×108 M☉ which are separated by around 0.33 pc and orbit each other with a period of 480 years. The second black hole pertubates the accretion disk, resulting to fluctuations in activity.[11] The X-rays observations indicate that the nuclear region is hidden behind a compton thick absorber with a column density of NH ≃ 1025 cm−2 that covers 75% to 85% of the X-rays source.[12]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 "NASA/IPAC Extragalactic Database". Results for 3C 345. https://ned.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=3C+345&extend=no. 
  2. ↑ Pötzl, F. M.; Lobanov, A. P.; Ros, E.; Gómez, J. L.; Bruni, G.; Bach, U.; Fuentes, A.; Gurvits, L. I. et al. (April 2021). "Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron: IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature". Astronomy & Astrophysics 648: A82. doi:10.1051/0004-6361/202039493. 
  3. ↑ 3.0 3.1 3.2 3.3 Zensus, J. A.; Cohen, M. H.; Unwin, S. C. (April 1995). "The Parsec-scale jet in quasar 3C 345". The Astrophysical Journal 443: 35. doi:10.1086/175501. https://articles.adsabs.harvard.edu/pdf/1995ApJ...443...35Z. 
  4. ↑ Kirhakos, Sofia; Bahcall, John N.; Schneider, Donald P.; Kristian, Jerome (20 July 1999). "The Host Galaxies of Three Radio‐loud Quasars: 3C 48, 3C 345, and B2 1425+267". The Astrophysical Journal 520 (1): 67–77. doi:10.1086/307430. 
  5. ↑ 5.0 5.1 Kharb, P.; Lister, M. L.; Marshall, H. L.; Hogan, B. S. (1 April 2012). "Chandra and HST imaging of the Quasars PKS B0106+013 and 3C 345: Inverse Compton X-Rays and Magnetized Jets". The Astrophysical Journal 748 (2): 81. doi:10.1088/0004-637X/748/2/81. 
  6. ↑ 6.0 6.1 6.2 Schinzel, F. K.; Lobanov, A. P.; Taylor, G. B.; Jorstad, S. G.; Marscher, A. P.; Zensus, J. A. (January 2012). "Relativistic outflow drives γ -ray emission in 3C 345". Astronomy & Astrophysics 537: A70. doi:10.1051/0004-6361/201117705. 
  7. ↑ "ATel #11624: Bright optical outbursts of the FSRQ Ton 599 and 3C 345". 9 May 2018. https://www.astronomerstelegram.org/?read=11624. 
  8. ↑ "ATel #10453: Fermi LAT detection of a bright GeV gamma-ray flare from the FSRQ 3C 345". 2 June 2017. https://www.astronomerstelegram.org/?read=10453. 
  9. ↑ Berton, M.; Liao, N. H.; La Mura, G.; Järvelä, E.; Congiu, E.; Foschini, L.; Frezzato, M.; Ramakrishnan, V. et al. (June 2018). "The flat-spectrum radio quasar 3C 345 from the high to the low emission state". Astronomy & Astrophysics 614: A148. doi:10.1051/0004-6361/201731625. 
  10. ↑ Lobanov, Andrew P.; Zensus, J. Anton (20 August 1999). "Spectral Evolution of the Parsec‐Scale Jet in the Quasar 3C 345". The Astrophysical Journal 521 (2): 509–525. doi:10.1086/307555. 
  11. ↑ Lobanov, A. P.; Roland, J. (March 2005). "A supermassive binary black hole in the quasar 3C 345". Astronomy & Astrophysics 431 (3): 831–846. doi:10.1051/0004-6361:20041831. https://www.aanda.org/10.1051/0004-6361:20041831/pdf. 
  12. ↑ Eguchi, Satoshi (July 2017). "Compton thick absorber in type 1 quasar 3C 345 revealed by Suzaku and Swift/BAT". Monthly Notices of the Royal Astronomical Society 468 (4): 4529–4538. doi:10.1093/mnras/stx754. 

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