Accession Number : ADA583442

Title :   Herschel-PACS Observations of Far-IR CO Line Emission in NGC 1068: Highly Excited Molecular Gas in the Circumnuclear Disk

Descriptive Note : Journal article


Personal Author(s) : Hailey-Dunsheath, S ; Sturm, E ; Fischer, J ; Sternberg, A ; Gracia-Carpio, J ; Davies, R ; Gonzalez-Alfonso, E ; Mark, D ; Poglitsch, A ; Contursi, A

Full Text :

Report Date : 10 Aug 2012

Pagination or Media Count : 21

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)/kappa(B) = 580-2565 Kappa) range, all of which are consistent with arising from within the central 10 (700 pc). 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 approx. 80 km s(-1). We employ a large velocity gradient model and derive Eta(H2) approx. 10(5.6) cm(-3), T(kin) approx. 170 K, and M(H2) approx. 10(6.7) M for the ME component and eta(H2) approx. 10(6.4) cm(-3), T(kin) approx. 570 K, and M(H2) approx. 10(5.6) M for the HE component, although for both components the uncertainties in the density and mass are plus or minus (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 the approx. 200 pc 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 H(2) ring, but a better kinematic match is found with a clump of infalling gas approx. 40 pc 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.


Subject Categories : Astronomy
      Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE