Graduate Research Seminar I/II

A precessing molecular jet signaling an obscured, growing SMBH in NGC1377?

Daniel Wysocki • • journal_club


“A precessing molecular jet signaling an obscured, growing supermassive black hole in NGC1377?” by Aalto et al.


Observed high velocity, collimated nuclear outflow from NGC1377, interpreted as a jet. Simple model of precessing nuclear jet fit the observations well (Figure 5). Two likely causes are an SMBH binary, and gas flow with misaligned angular momentum onto warped accretion disk.


Data obtained with ALMA. Used 1.875 GHz bandwidth centered at 344.0 GHz to observe CO 3–2 lines, and 354.3 GHz to observe HCO+ 4–3 and HCN 4–3 lines. Two 2 GHz bandwidth continuum observations centered at 342.2 and 356 GHz.


Precession is the simplest explanation of velocity variations in PV diagram in Figure 3, and is supported by model in Figure 5.

Several possible causes of precession.

  1. warped accretion disk
    • misalignment between SMBH spin and surrounding accretion disk
    • accretion flow transporting in gas of misaligned angular momentum
  2. SMBH binary system
    • geodetic precession of primary SMBH spin axis misaligned with binary total angular momentum
    • or inner disk precession (tidal interaction of inclined secondary SMBH)
    • binary system further suggested by post-starburst optical spectrum
      • suggests aging (1Gyr) starburst
      • may be linked with merger event
      • dynamical effects of merger subsided, binary SMBH left behind

No Precession?

Precession is not the only possible explanation for velocity variations in PV diagram in Figure 3.

  1. orbiting object
    • single jet from one of two SMBHs in a binary
    • or combination of two jets from two SMBHs in a binary
  2. bicone projection
    • apparent precession is only a projection effect from bicone
    • Figure 6 contradicts this, does not match predictions from projection

SMBH Binary Implications

If precession is caused by binary SMBH system, has certain implications on coalescence. Presence of nuclear gas and dust concentration, combined with precessing molecular jet can aid coalescence of SMBHs, thereby overcoming the final parsec problem.