Molecular hydrogen and [Fe ii] in active galactic nuclei – III. Low-ionization nuclear emission-line region and star-forming galaxies

Abstract

We study the kinematics and excitation mechanisms of H 2 and [Fe II] lines in a sample of 67 emission-line galaxies with Infrared Telescope Facility SpeX near-infrared (0.8-2.4 μm) spectroscopy together with new photoionization models. H 2 emission lines are systematically narrower than narrow-line region lines, suggesting that the two are, very likely, kinematically disconnected. The new models and emission-line ratios show that the thermal excitation plays an important role not only in active galactic nuclei but also in star-forming galaxies. The importance of the thermal excitation in star-forming galaxies may be associated with the presence of supernova remnants close to the region emitting H 2 lines. This hypothesis is further supported by the similarity between vibrational and rotational temperatures of H 2 . We confirm that the diagram involving the line ratios H 2 2.121 μm/Brγ and [Fe II] 1.257 μm/Paβ is an efficient tool for separating emission-line objects according to their dominant types of activities. We suggest new limits to the line ratios in order to discriminate between the different types of nuclear activities.

Shutting down or powering up a (U)LIRG? Merger components in distinctly different evolutionary states in IRAS 19115−2124 (the Bird)

“…The Head and Tail locations have Trot ∼ 1000 , whilte Trot ∼ 2000 K at the Heart and Body nuclei. The vibrational temperatures are systematically higher everywhere T vib ∼ 3000−4000 K. Riffel et al (2013) find similar trends in their starburst LIRGs. The differences between Trot and T vib , as well as the line-ratios involving ν = 1 and ν = 2 transitions, indicate (see e.g.…”

“…For this case, since the extinction correction become quite significant between the J and K-band datacubes, the per spaxel corrections becomes too noisy and we adopt the extinction correction using the AV (Brγ / Paα) values in the Table 3 for the three regions separately. The three Bird components separate remarkably well in this diagnostic, which is used as an ionisation source indicator in a similar vein than BPT diagrams in the optical (Riffel et al 2013;Larkin et al 1998). The diagram progresses from young star formation ionisation at lower left, through AGN related ionisation in the middle to shock ionisation at upper right, with recent SN activity showing up at high [Fe II] / Paβ values.…”

A low-luminosity type-1 QSO sample

“…Right: diagnostic diagram with line ratios 1-0S (1) T vib ≈ T rot . In particular, Rodríguez-Ardila et al (2005) and Riffel et al (2013) show that star forming galaxies show T vib T rot while AGNs and LINERs tend to have similar values for T vib and T rot . In HE 1029-1831, the temperatures differ significantly from each other.…”

Shock Excited Molecules in NGC 1266: Ulirg Conditions at the Center of a Bulge-Dominated Galaxy

“…The line fluxes and errors associated with the continuum uncertainty are listed in Table 1, which also includes ground based measurements of 12 CO J = (1-0), (2-1), and (3-2) from Alatalo et al (2011). In addition to the H 2 lines from Spitzer IRS, we also add NIR 1-0 S(1) H 2 fluxes from Riffel et al (2013).…”