Molecular gas and dust in NGC 4550

Wiklind, T.; Henkel, C.

doi:10.1051/0004-6361:20010860

Cited by 17 publications

(21 citation statements)

References 33 publications

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“…(2) T kin > 50 K is also not likely because of the temperature deduced from [Ci] and the close association of CO and Ci, which appears to be independent of the environment (e.g., Ikeda et al 2002;Zhang et al 2007 local galactic disk (Weiß et al 2005), the [ 12 CO]/[H 2 ] abundance ratio should be of order 10 −4 (e.g., Frerking et al 1982). The resulting velocity gradient of dv/dr = 10 3 km s −1 pc −1 would be far too large in view of the measured line width (e.g., Weiß et al 2003) and the kinetic temperature such extreme conditions would induce (e.g., Wiklind & Henkel 2001). A velocity gradient of a few km −1 pc −1 is more realistic as, e.g., obtained from clouds in virial equilibrium for densities of order 10 4 cm −3 (Goldsmith 2001;his Eq.…”

Section: Large Velocity Gradient Model Calculationsmentioning

confidence: 99%

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Henkel¹,

Downes

Weiß³

et al. 2010

A&A

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Observations of 12 CO at high redshift indicate rapid metal enrichment in the nuclear regions of at least some galaxies in the early universe. However, the enrichment may be limited to nuclei that are synthesized by short-lived massive stars, excluding classical "secondary" nuclei like 13 C. Testing this idea, we used the IRAM Interferometer to tentatively detect the 13 CO J = 3 → 2 line at a level of 0.3 Jy km s −1 toward the Cloverleaf quasar at z = 2.5. This is the first observational evidence for 13 C at high redshift. The 12 CO/ 13 CO J = 3 → 2 luminosity ratio is with 40 +25 −8 much higher than ratios observed in molecular clouds of the Milky Way and in the ultraluminous galaxy Arp 220, but may be similar to that observed toward NGC 6240. Large Velocity Gradient models simulating seven 12 CO transitions and the 13 CO line yield 12 CO/ 13 CO abundance ratios in excess of 100. It is possible that the measured ratio is affected by a strong submillimeter radiation field, which reduces the contrast between the 13 CO line and the background. It is more likely, however, that the ratio is caused by a real deficiency of 13 CO. This is already apparent in local ultraluminous galaxies and may be even more severe in the Cloverleaf because of its young age ( < ∼ 2.5 Gyr). A potential conflict with optical data, indicating high abundances also for secondary nuclei in quasars of high redshift, may be settled if the bulk of the CO emission is originating sufficiently far from the active galactic nucleus of the Cloverleaf.

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Section: Large Velocity Gradient Model Calculationsmentioning

confidence: 99%

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Henkel¹,

Downes

Weiß³

et al. 2010

A&A

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“…Higher mass galaxies do host more hot X-ray gas, which could inhibit the formation of large amounts of dense molecular gas (Wiklind & Henkel 2001;O'Sullivan et al 2001;Sarzi et al 2006). Albeit on much larger scales, there are documented differences in the properties of molecular disks in elliptical and spiral galaxies.…”

Section: Environmental Effectsmentioning

confidence: 99%

Toward Precision Supermassive Black Hole Masses Using Megamaser Disks

Bosch

Greene

Braatz

et al. 2016

ApJ

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Megamaser disks provide the most precise and accurate extragalactic supermassive black hole (BH) masses. Here we describe a search for megamasers in nearby galaxies using the Green Bank Telescope (GBT). We focus on galaxies where we believe that we can resolve the gravitational sphere of influence of the BH and derive a stellar or gas dynamical measurement with optical or NIR observations. Since there are only a handful of super massive BHs that have direct BH mass measurements from more than one method, even a single galaxy with a megamaser disk and a stellar dynamical BH mass would provide necessary checks on the stellar dynamical methods. We targeted 87 objects from the Hobby-Eberly Telescope Massive Galaxy Survey, and detected no new maser disks. Most of the targeted objects are elliptical galaxies with typical stellar velocity dispersions of 250 km s −1 and distances within 130 Mpc. We discuss the implications of our non-detections, whether they imply a threshold X-ray luminosity required for masing, or possibly reflect the difficulty of maintaining a masing disk around much more massive ( 10 8  M  ) BHs at a low Eddington ratio. Given the power of maser disks for probing BH accretion and demographics, we suggest that future maser searches should endeavour to remove remaining sample biases, in order to sort out the importance of these covariant effects.

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“…An irregular dust distribution is also observed within the central 20 arcsec in diameter. The dust is distributed in clumpy arcs and is stronger on the northern half of the galaxy (Wiklind & Henkel 2001). H i observations have not detected neutral gas in NGC 4550, the strictest upper limit being 7 × 10 7 M ⊙ from Duprie & Schneider (1996).…”

Section: Introductionmentioning

confidence: 99%

“…H i observations have not detected neutral gas in NGC 4550, the strictest upper limit being 7 × 10 7 M ⊙ from Duprie & Schneider (1996). Molecular gas was first discovered in NGC 4550 by Wiklind & Henkel (2001) using the Institut de Radioastronomie Millimétrique (IRAM) 30‐m telescope. They reported a small mass of molecular gas, 1.3 × 10 7 M ⊙ , noting that the distribution of the molecular gas is likely to resemble that of the dust, due to a strong asymmetry in the observed CO emission line towards positive relative velocities.…”

Section: Introductionmentioning

confidence: 99%

Molecular gas and star formation in the red-sequence counter-rotating disc galaxy NGC 4550

Crocker

Jeong

Komugi

et al. 2009

Monthly Notices of the Royal Astronomical Society

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We present observations of the CO(1‐0) emission in the central 750 pc (10 arcsec) of the counter‐rotating disc galaxy NGC 4550, obtained at the Institut de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer. Very little molecular gas is detected, only 1×107 M⊙, and its distribution is lopsided, with twice as much molecular gas observed at positive relative velocities than at negative relative velocities. The velocity gradient in the CO(1‐0) emission shows that the molecular gas rotates like the thicker of the two stellar discs, which is an unexpected alignment of rotations if the thinner disc was formed by a major gas accretion event. However, a simulation shows that the gas rotating like the thicker disc naturally results from the coplanar merger of two counter‐rotating disc galaxies, demonstrating the feasibility of this scenario for the formation of NGC 4550. We investigate various star formation tracers to determine whether the molecular gas in NGC 4550 is currently forming stars. Ultraviolet (UV) imaging data and optical absorption line strengths both suggest a recent star formation episode; the best‐fitting two‐population model to the UV‐optical colours yields a mass of young stars of 5.9×107 M⊙ with an age of 280 Myr. The best information on the current star formation rate is a far‐infrared‐based upper limit of only 0.02 M⊙ yr−1. We are thus witnessing NGC 4550 either in a dip within a bursty star formation period or during a more continuous low‐level star formation episode.

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Molecular gas and dust in NGC 4550

Cited by 17 publications

References 33 publications

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Toward Precision Supermassive Black Hole Masses Using Megamaser Disks

Molecular gas and star formation in the red-sequence counter-rotating disc galaxy NGC 4550

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Molecular gas and dust in NGC 4550

Cited by 17 publications

References 33 publications

Weak13CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Weak13CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Toward Precision Supermassive Black Hole Masses Using Megamaser Disks

Molecular gas and star formation in the red-sequence counter-rotating disc galaxy NGC 4550

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Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst