HERSCHEL-PACS OBSERVATIONS OF FAR-IR CO LINE EMISSION IN NGC 1068: HIGHLY EXCITED MOLECULAR GAS IN THE CIRCUMNUCLEAR DISK

Hailey-Dunsheath, S; Sturm, E; Fischer, J; Sternberg, A; Gracia-Carpio, J; Davies, R; Gonzalez-Alfonso, E; Mark, D; Poglitsch, A; Contursi, A; Genzel, R; Lutz, D; Tacconi, L; Veilleux, S; Verma, A; de Jong, J

Journal article

HERSCHEL-PACS OBSERVATIONS OF FAR-IR CO LINE EMISSION IN NGC 1068: HIGHLY EXCITED MOLECULAR GAS IN THE CIRCUMNUCLEAR DISK

Abstract:: We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 11 transitions in the J upper = 14-30 (E upper/kB = 580-2565K) range, all of which are consistent with arising from within the central 10″ (700pc). The detected transitions are modeled as arising from two different components: a moderate-excitation (ME) component close to the galaxy systemic velocity and a high-excitation (HE) component that is blueshifted by 80kms-1. We employ a large velocity gradient model and derive n H2 105.6cm-3, T kin 170K, and M H2 106.7 M ⊙ for the ME component and n H2 106.4cm-3, T kin 570K, and M H2 105.6 M ⊙ for the HE component, although for both components the uncertainties in the density and mass are ±(0.6-0.9)dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution and find that the ME transitions are consistent with these lines arising in the200pc diameter ring of material traced by H 2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H2 ring, but a better kinematic match is found with a clump of infalling gas 40pc north of the active galactic nucleus (AGN). We consider potential heating mechanisms and conclude that X-ray- or shock heating of both components is viable, while far-UV heating is unlikely. We discuss the prospects of placing the HE component near the AGN and conclude that while the moderate thermal pressure precludes an association with the 1pc radius H2O maser disk, the HE component could potentially be located only a few parsecs more distant from the AGN and might then provide the N H 1025cm-2 column obscuring the nuclear hard X-rays. Finally, we also report sensitive upper limits extending up to J upper = 50, which place constraints on a previous model prediction for the CO emission from the X-ray obscuring torus. © 2012 The American Astronomical Society. All rights reserved.

Publication status:: Published

Actions

Email

Email this record

Send the bibliographic details of this record to your email address.

Your Email
Please enter the email address that the record information will be sent to.

-
Your message (optional)
Please add any additional information to be included within the email.
Share
Cite

Cite this record

APA Style

Hailey-Dunsheath, S., Sturm, E., Fischer, J., Sternberg, A., Gracia-Carpio, J., Davies, R., Gonzalez-Alfonso, E., Mark, D., Poglitsch, A., Contursi, A., Genzel, R., Lutz, D., Tacconi, L., Veilleux, S., Verma, A., & de Jong, J. (2012). HERSCHEL-PACS OBSERVATIONS OF FAR-IR CO LINE EMISSION IN NGC 1068: HIGHLY EXCITED MOLECULAR GAS IN THE CIRCUMNUCLEAR DISK. ASTROPHYSICAL JOURNAL, 755(1), 57–57.

MLA Style

Hailey-Dunsheath, S, et al. “HERSCHEL-PACS OBSERVATIONS OF FAR-IR CO LINE EMISSION IN NGC 1068: HIGHLY EXCITED MOLECULAR GAS IN THE CIRCUMNUCLEAR DISK.” ASTROPHYSICAL JOURNAL, vol. 755, no. 1, 2012, pp. 57–57.

Chicago Style

Hailey-Dunsheath, S, E Sturm, J Fischer, et al. 2012. “HERSCHEL-PACS OBSERVATIONS OF FAR-IR CO LINE EMISSION IN NGC 1068: HIGHLY EXCITED MOLECULAR GAS IN THE CIRCUMNUCLEAR DISK.” ASTROPHYSICAL JOURNAL 755 (1): 57–57.
Print