Molecular Absorption in Cen a on Vlbi Scales

Langevelde, H. J. van; Pihlstroem, Y. M.; Beasley, A. J.

doi:10.1007/s10509-005-3699-5

Cited by 3 publications

(4 citation statements)

References 7 publications

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“…Given the very small apparent size of the continuum source at millimeter wavelengths, we expect the continuum source to be completely covered by the absorbing clouds, and will assume a filling factor of unity in our analysis. This assumption is supported by VLBA data of the OH 18 cm absorption, which appears to cover a large fraction the continuum source (van Langevelde et al 2005).…”

Section: Continuum Background and Filling Factormentioning

confidence: 65%

HCO⁺AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

Müller

Dinh-V-Trung

2009

ApJ

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We have investigated the presence of dense gas toward the radio source Cen A by looking at the absorption of the HCO + and HCN (3-2) lines in front of the bright continuum source with the Submillimeter Array. We detect narrow HCO + (3-2) absorption, and tentatively HCN (3-2), close to the systemic velocity. For both molecules, the J = 3 − 2 absorption is much weaker than for the J = 1 − 0 line. From simple excitation analysis, we conclude that the gas density is on the order of a few 10 4 cm −3 for a column density N (HCO + )/∆V of 3 × 10 12 cm −2 km −1 s and a kinetic temperature of 10 K. In particular, we find no evidence for molecular gas density higher than a few 10 4 cm −3 on the line of sight to the continuum source. We discuss the implications of our finding on the nature of the molecular gas responsible for the absorption toward Cen A.

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Section: Continuum Background and Filling Factormentioning

confidence: 65%

HCO⁺AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

Müller

Dinh-V-Trung

2009

ApJ

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“…≃ 51 • as the inner 21 cm jet extending up to 55 ′′ (van der Hulst et al 1983;Sarma et al 2002). Note that van Langevelde et al (2005) present a VLBI 18 cm continuum map with a subarcsecond resolution where the central bright component is seen. However, the rest of the nuclear jet is not as clearly detected as in our map.…”

Section: CM Continuum: Nuclear Jetmentioning

confidence: 92%

“…Molecular absorption lines from cm to submm wavelengths have also been detected for several species. At cm wavelengths narrow molecular lines (a few km s −1 width) close to the systemic velocity have been observed in several molecules such as OH, H 2 CO, C 3 H 2 and NH 3 (Gardner & Whiteoak 1976a,b;Seaquist & Bell 1990;van Langevelde et al 1995van Langevelde et al , 2005. Single-dish observations have been performed at mm/submm wavelengths for the lowest transitions of CO, HCN, HNC, HCO + , H 13 CO + , N 2 H + , C 2 H, CN and CS (Eckart et al 1990a;Israel et al 1990;Wiklind & Combes 1997;Eckart et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Disentangling the Circumnuclear Environs of Centaurus A. Ii. On the Nature of the Broad Absorption Line

Espada

Peck

Matsushita

et al. 2010

ApJ

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We report on atomic gas (H I) and molecular gas (as traced by CO(2-1)) redshifted absorption features toward the nuclear regions of the closest powerful radio galaxy, Centaurus A (NGC 5128). Our H I observations using the Very Long Baseline Array allow us to discern with unprecedented sub-parsec resolution H I absorption profiles toward different positions along the 21 cm continuum jet emission in the inner 0. ′′ 3 (or 5.4 pc). In addition, our CO(2-1) data obtained with the Submillimeter Array probe the bulk of the absorbing molecular gas with little contamination by emission, not possible with previous CO single-dish observations. We shed light with these data on the physical properties of the gas in the line of sight, emphasizing the still open debate about the nature of the gas that produces the broad absorption line (∼ 55 km s −1 ). First, the broad H I line is more prominent toward the central and brightest 21 cm continuum component than toward a region along the jet at a distance ∼ 20 mas (or 0.4 pc) further from it. This suggests that the broad absorption line arises from gas located close to the nucleus, rather than from diffuse and more distant gas. Second, the different velocity components detected in the CO(2-1) absorption spectrum match well other molecular lines, such as those of HCO + (1-0), except the broad absorption line that is detected in HCO + (1-0) (and most likely related to that of the H I). Dissociation of molecular hydrogen due to the AGN seems to be efficient at distances r 10 pc, which might contribute to the depth of the broad H I and molecular lines.

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“…Spectral line models enable high-precision measurements of the structure and kinetics of the various components of the studied sources, using different tracers [e.g. 29, 146], or by using absorption of continuum flux by intervening gas [155,109]. VLBI is the most developed area driving the demand for simultaneous mm-wavelength receivers, but it is not the only field.…”

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confidence: 99%

The science case for simultaneous mm-wavelength receivers in radio astronomy

Dodson¹,

Rioja²,

Gómez³

et al. 2017

New Astronomy Reviews

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This review arose from the European Radio Astronomy Technical Forum (ERATec) meeting held in Firenze, October 2015, and aims to highlight the breadth and depth of the high-impact science that will be aided and assisted by the use of simultaneous mm-wavelength receivers. Recent results and opportunities are presented and discussed from the fields of: continuum VLBI (observations of weak sources, astrometry, observations of AGN cores in spectral index and Faraday rotation), spectral line VLBI (observations of evolved stars and massive star-forming regions) and time domain observations of the flux variations arising in the compact jets of X-ray binaries. Our survey brings together a large range of important science applications, which will greatly benefit from simultaneous observing at mm-wavelengths. Such facilities are essential to allow these applications to become more efficient, more sensitive and more scientifically robust. In some cases without simultaneous receivers the science goals are simply unachievable. Similar benefits would exist in many other high frequency astronomical fields of research.

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Molecular Absorption in Cen a on Vlbi Scales

Cited by 3 publications

References 7 publications

HCO⁺AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

HCO⁺AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

Disentangling the Circumnuclear Environs of Centaurus A. Ii. On the Nature of the Broad Absorption Line

The science case for simultaneous mm-wavelength receivers in radio astronomy

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Molecular Absorption in Cen a on Vlbi Scales

Cited by 3 publications

References 7 publications

HCO+AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

HCO+AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

Disentangling the Circumnuclear Environs of Centaurus A. Ii. On the Nature of the Broad Absorption Line

The science case for simultaneous mm-wavelength receivers in radio astronomy

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HCO⁺AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

HCO⁺AND HCNJ= 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A