(C-13)O in IC 342 - Evidence for a spiral density wave in the nucleus

Turner, Jean L.; Hurt, Robert L.

doi:10.1086/170852

Cited by 61 publications

(80 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on measurements at various frequencies, previous works have concluded that thermal free-free bremsstrahlung should dominate the emission budget at 3.5 mm (Downes et al 1992;Turner & Ho 1983;Turner & Hurt 1992). The good spatial coincidence between the 3.5 mm and the Hα emissions supports the conclusion that the 3.5 mm emission traces the location of ongoing star formation in the inner r ∼ 80 pc of IC 342.…”

Section: The 35 MM Continuum Mapmentioning

confidence: 70%

Large-scale molecular shocks in galaxies: the SiO interferometer map of IC 342

Usero

García‐Burillo

Martı́n-Pintado³

et al. 2006

A&A

View full text Add to dashboard Cite

We present the first high-resolution (5. 6 × 5. 1) images of the emission of silicon monoxide (SiO) in the nucleus of the nearby spiral IC 342, obtained with the IRAM Plateau de Bure Interferometer (PdBI). Using a two-field mosaic, we have simultaneously mapped the emission of the SiO(v = 0, J = 2−1) and H 13 CO + (J = 1−0) lines in a region of ∼0.9 kpc × 1.3 kpc (RA × Dec) centered around the nucleus of IC 342. The bulk of the emission in the two lines comes from a ∼290 pc spiral arm located to the North and a central component that forms the southern ridge of a r ∼ 80 pc nuclear ring that was identified in other interferometer maps of the galaxy. We detect continuum emission at 86.8 GHz in a ∼80−180 pc central source. The continuum emission, dominated by thermal free-free bremsstrahlung, is mostly anticorrelated with the observed distribution of SiO clouds. The SiO-to-H 13 CO + intensity ratio is seen to increase by an order of magnitude from the nuclear ring (∼0.3) to the spiral arm (∼3.3). Furthermore the gas kinematics show significant differences between SiO and H 13 CO + over the spiral arm, where the linewidths of SiO are a factor of 2 larger than those of H 13 CO + . The average abundance of SiO in the inner r ∼ 320 pc of IC 342 is X(SiO) 2 × 10 −10 . This shows that shock chemistry is at work in the inner molecular gas reservoir of IC 342. To shed light on the nature of shocks in IC 342, we have compared the emission of SiO with another tracer of molecular shocks: the emission of methanol (CH 3 OH). We find that the significant difference of the abundance of SiO measured between the spiral arm (X(SiO) ∼ a few 10 −9 ) and the nuclear ring (X(SiO) ∼ 10 −10 ) is not echoed by a comparable variation in the SiO-to-CH 3 OH intensity ratio. This implies that the typical shock velocities should be similar in the two regions. In contrast, the fraction of shocked molecular gas should be ∼5−7 times larger in the spiral arm (up to ∼10% of the available molecular gas mass over the arm region) compared to the nuclear ring. In the light of these results, we revise the validity of the various scenarios that have been proposed to explain the onset of shock chemistry in galaxies and study their applicability to the nucleus of IC 342. We conclude that the large-scale shocks revealed by the SiO map of IC 342 are mostly unrelated to star formation and arise instead in a pre-starburst phase. Shocks are driven by cloud-cloud collisions along the potential well of the IC 342 bar. The general implications for the current understanding of galaxy evolution are discussed.

show abstract

Section: The 35 MM Continuum Mapmentioning

confidence: 70%

Large-scale molecular shocks in galaxies: the SiO interferometer map of IC 342

Usero

García‐Burillo

Martı́n-Pintado³

et al. 2006

A&A

View full text Add to dashboard Cite

show abstract

“…Both have extended bar-like arms that terminate on a central ring that is actively forming stars. The molecular gas morphology of IC 342 is consistent with that of a gaseous bar (Turner & Hurt 1992). However, because of the very small central ring and ambiguous kinematics, other conclusions including unbarred spiral arms coupled with massive star feedback remain feasible (Schinnerer et al 2008).…”

Section: Relative Shock Tracer Morphologies and Bar Propertiesmentioning

confidence: 72%

Spatially Resolved Chemistry in Nearby Galaxies. Ii. The Nuclear Bar in Maffei 2

Meier

Turner

2012

ApJ

Self Cite

View full text Add to dashboard Cite

We present 2 ′′ -10 ′′ imaging of eleven transitions from nine molecular species across the nuclear bar in Maffei 2. The data were obtained with the BIMA and OVRO interferometers. The ten detected transitions are compared with existing CO isotopologues, HCN, CS and millimeter continuum data. Dramatic spatial variations among the mapped species are observed across the nuclear bar. A principle component analysis is performed to characterize correlations between the transitions, star formation and molecular column density. The analysis reveals that HCN, HNC, HCO + and 3 mm continuum are tightly correlated, indicating a direct connection to massive star formation. We find two main morphologically distinct chemical groups, CH 3 OH, SiO and HNCO comprising the grain chemistry molecules, versus HCN, HNC, HCO + and C 2 H, molecules strong in the presence of star formation. The grain chemistry molecules, HNCO, CH 3 OH and SiO, trace hydrodynamical bar shocks. The near constancy of the HNCO/CH 3 OH, SiO/CH 3 OH and SiO/HNCO ratios argue that shock properties are uniform across the nucleus. HCN/HCO + , HCN/HNC, HCN/CS and HCN/CO ratios are explained primarily by variations in density. High HCO + /N 2 H + ratios are correlated with the C 2 H line, suggesting that this ratio may be a powerful new dense photon-dominated region (PDR) probe in external galaxies. C 2 H reveals a molecular outflow along the minor axis. The morphology and kinematics of the outflow are consistent with an outflow age of 6-7 Myrs.

show abstract

“…-which is usually interpreted to trace predominantly intercloud material -is very closely correlated to the HCN emission, whereas the map of 13 CO (1-0) emission (5 resol.) by Turner & Hurt (1992) does not show the prominent HCN cloud "B" which is stated to be correlated to strong H II radio continuum emission. This picture gets even more complex regarding the NH 3 map (5 resol.)…”

Section: Introductionmentioning

confidence: 85%

The nucleus of the nearby galaxy IC 342

Schulz

Güsten

Køster

et al. 2001

A&A

View full text Add to dashboard Cite

Abstract.To study the different components of the molecular gas in the nuclear region of the nearby spiral galaxy IC 342, 12 CO (3-2), 13 CO (3-2) and (2-1), as well as HCN (1-0) through (4-3) observations are presented and analyzed in conjunction with a variety of line and continuum emission data of the literature. We find several giant molecular clouds embedded in a medium with lower column and volume density. The gas shows strong density and temperature gradients with a very clumpy substructure; the lower-density gas is rather warm (≤50 K) and the temperature decreases with increasing density. While LVG calculations are contradicting our observations, we are able to explain all CO and [C II] line data by applying a model of photon dominated regions (PDR); for the gas seen in these lines we find no evidence for an additional dominant heating mechanism. On the other hand, for our HCN observations tracing the dense gas clumps (n (H2) ≈ 10 6 cm −3 ) where the influence of UV photons is expected to be less important than for less dense gas seen in CO (n (H2) ≈ 10 4 cm −3 ), an LVG model approach should be applicable and, in fact, yields results which fit well the data and support the outlined scenario. For this gas component which is rather cool (T k ≤ 30 K), heating processes involving photoelectrons should be unimportant and other mechanisms like turbulent energy dissipation or cosmic rays should be considered. The structure of the nucleus of IC 342 with several giant molecular clouds with sizes of ≤20 to 50 pc and masses of order 10 6 M partly associated with H II regions and embedded into a lower-density interstellar medium shows striking similarities in terms of cloud distribution and their physical behaviour with our Galactic Centre region.

show abstract

(C-13)O in IC 342 - Evidence for a spiral density wave in the nucleus

Cited by 61 publications

References 0 publications

Large-scale molecular shocks in galaxies: the SiO interferometer map of IC 342

Large-scale molecular shocks in galaxies: the SiO interferometer map of IC 342

Spatially Resolved Chemistry in Nearby Galaxies. Ii. The Nuclear Bar in Maffei 2

The nucleus of the nearby galaxy IC 342

Contact Info

Product

Resources

About