Mid-infrared imaging of active galaxies

Galliano, E.; Alloin, D.; Pantin, E.; Lagage, Pierre-Olivier; Marco, Olivier

doi:10.1051/0004-6361:20053049

Cited by 96 publications

(187 citation statements)

References 69 publications

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“…Millimeter/sub-millimeter and mid-IR high spatial resolution observations of the nuclear region of NGC 1068 support the classical picture of a rotating torus (e.g., Tacconi et al 1994;Schinnerer et al 2000;Galliano et al 2005;Poncelet et al 2007). However, in some previous works (e.g., Schinnerer et al 2000) it was speculated that the classical (large-scale) molecular torus is not always needed to explain the occultation of the nuclear regions.…”

Section: Structure Of the Cnd And Limitations Of The Modelmentioning

confidence: 55%

Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-Jlines of dense gas tracers

Pérez-Beaupuits¹,

Spaans²,

Tak

et al. 2009

A&A

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Context. Single-dish observations of molecular tracers have suggested that both star formation and an AGN can drive the gas chemistry of the central ∼kpc of active galaxies. The irradiation by UV photons from an starburst or by X-rays from an AGN is expected to produce different signatures in molecular chemistry, which existing data on low-J lines cannot distinguish, as they do not trace gas at high temperature and density. Depending on the angular scale of a galaxy, the observed low-J lines can be dominated by the emission coming from the starburst ring rather than from the central region. Aims. With the incorporation of high-J molecular lines, we aim to constrain the physical conditions of the dense gas in the central region of the Seyfert 2 galaxy NGC 1068 and to determine signatures of the AGN or the starburst contribution. Methods. We used the James Clerk Maxwell Telescope to observe the J = 4−3 transition of HCN, HNC, and HCO + , as well as the CN N J = 2 5/2 − 1 3/2 and N J = 3 5/2 − 2 5/2 , in NGC 1068. We estimate the excitation conditions of HCN, HNC, and CN, based on the line intensity ratios and radiative transfer models. We discuss the results in the context of models of irradiation of the molecular gas by UV light and X-rays. Results. A first-order estimate leads to starburst contribution factors of 0.58 and 0.56 for the CN and HCN J = 1−0 lines, respectively. We find that the bulk emission of HCN, HNC, CN, and the high-J HCO + emerge from dense gas (n(H 2 ) ≥ 10 5 cm −3 ). However, the low-J HCO + lines (dominating the HCO + column density) trace less dense (n(H 2 ) < 10 5 cm −3 ) and colder (T K ≤ 20 K) gas, whereas the high-J HCO + emerges from warmer (>30 K) gas than the other molecules. We also find that the HNC/HCN and CN/HCN line intensity ratios decrease with increasing rotational quantum number J.

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Section: Structure Of the Cnd And Limitations Of The Modelmentioning

confidence: 55%

Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-Jlines of dense gas tracers

Pérez-Beaupuits¹,

Spaans²,

Tak

et al. 2009

A&A

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“…flip from near-to mid-IR wavelengths, with the factor ∼2.5 increase in spatial resolution providing a more accurate and consistent result. Galliano et al (2003Galliano et al ( , 2005 We discount directly observed synchrotron radiation from the radio jet accounting for the polarization, as an extrapolation of the radio emission to the mid-IR provides too little flux. Hence, these data confirm that the extended mid-IR polarized emission north of the nucleus is mostly from dust in the ionization cone.…”

Section: Discussionmentioning

confidence: 99%

Gemini Mid-IR Polarimetry of NGC 1068: Polarized Structures around the Nucleus

Packham¹,

Young²,

Fisher³

et al. 2007

ApJ

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We present diffraction-limited, 10 mm imaging polarimetry data for the central regions of the archetypal Seyfert active galactic nucleus NGC 1068. The position angle of polarization is consistent with three dominant polarizing mechanisms. We identify three distinct regions of polarization: (1) north of the nucleus, arising from aligned dust in the narrow emission line region, (2) south, east, and west of the nucleus, consistent with dust being channeled toward the central engine, and (3) a central minimum of polarization consistent with a compact (≤22 pc) torus. These observations provide continuity between the geometrically and optically thick torus and the host galaxy's nuclear environments. These images represent the first published mid-IR polarimetry from an 8 m-class telescope and illustrate the potential of such observations.

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“…For NGC 1365, Sakamoto et al (2007) found five CO hot spots with line widths (FWHM) between 60 and 90 km s −1 that seem to be associated with SSCs of ∼10 6 M (Galliano et al 2005). Hsieh et al (2011) found many GMAs in the molecular ring (14 GMAs) and the dust lane (5 GMAs) of NGC 1097.…”

Section: Gmas In Galaxies With Nuclear Molecular Ringsmentioning

confidence: 97%

The NGC 1614 interacting galaxy

König

Aalto

Müller

et al. 2013

A&A

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Minor mergers frequently occur between giant and gas-rich low-mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power active galactic nuclei (AGN) in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in the starburst minor merger NGC 1614, whose molecular medium we explore at half-arcsecond angular resolution through our observations of 12 CO (2−1) emission using the Submillimeter Array (SMA). We compare our 12 CO (2−1) maps with optical and Paα, Hubble Space Telescope and high angular resolution radio continuum images to study the relationships between dense molecular gas and the NGC 1614 starburst region. The most intense 12 CO emission occurs in a partial ring with ∼230 pc radius around the center of NGC 1614, with an extension to the northwest into the dust lane that contains diffuse molecular gas. We resolve ten giant molecular associations (GMAs) in the ring, which has an integrated molecular mass of ∼8 × 10 8 M . Our interferometric observations filter out a large part of the 12 CO (1−0) emission mapped at shorter spacings, indicating that most of the molecular gas is diffuse and that GMAs only exist near and within the circumnuclear ring. The molecular ring is uneven with most of the mass on the western side, which also contains GMAs extending into a pronounced tidal dust lane. The spatial and kinematic patterns in our data suggest that the northwest extension of the ring is a cosmic umbilical cord that is feeding molecular gas associated with the dust lane and tidal debris into the nuclear ring, which contains the bulk of the starburst activity. The astrophysical process for producing a ring structure for the final resting place of accreted gas in NGC 1614 is not fully understood, but the presence of numerous GMAs suggests an orbit-crowding or resonance phenomenon. There is some evidence that star formation is progressing radially outward within the ring, indicating that a self-triggering mechanism may also affect star formation processes. The net result of this merger therefore very likely increases the central concentration of stellar mass in the NGC 1614 remnant giant system.

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Mid-infrared imaging of active galaxies

Cited by 96 publications

References 69 publications

Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-Jlines of dense gas tracers

Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-Jlines of dense gas tracers

Gemini Mid-IR Polarimetry of NGC 1068: Polarized Structures around the Nucleus

The NGC 1614 interacting galaxy

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