Structure and chemistry in the hot molecular core G34.3+0.15

Macdonald, G. H.; Habing, R. J.; Millar, T. J.

doi:10.1007/bf00667841

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…Several studies have been made to investigate the chemistry of HMCs (Macdonald et al 1995;Gibb et al 2000;Nomura & Millar 2004;Garrod & Herbst 2006). Charnley et al (1992) showed that initial differences in the chemical composition and gas phase reactions subsequent to evaporation from dust grains can explain the existence of many of the complex O-and N-bearing species.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of complex N- and O-bearing molecules in hot molecular cores

Fontani

Pascucci

Caselli

et al. 2007

A&A

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Aims. We have observed several emission lines of two Nitrogen-bearing (C 2 H 5 CN and C 2 H 3 CN) and two Oxygen-bearing (CH 3 OCH 3 and HCOOCH 3 ) molecules towards a sample of well-known hot molecular cores (HMCs) in order to check whether the chemical differentiation seen in the Orion-HMC and W3(H 2 O) between O-and N-bearing molecules is a general property of HMCs. Methods. With the IRAM-30m telescope we have observed 12 HMCs in 21 bands, centered at frequencies from 86 250 to 258 280 MHz. Results. In six sources, we have detected a number of transitions sufficient to derive their main physical properties. The rotational temperatures obtained from C 2 H 5 CN, C 2 H 3 CN and CH 3 OCH 3 range from ∼100 to ∼150 K in these HMCs. The total column densities of these molecules are of the order of ∼10 15 −10 17 cm −2 . Single Gaussian fits performed to unblended lines show a marginal difference in the line peak velocities of the C 2 H 5 CN and CH 3 OCH 3 lines, indicating a possible spatial separation between the region traced by the two molecules. On the other hand, neither the linewidths nor the rotational temperatures and column densities confirm such a result. The average molecular abundances of C 2 H 5 CN, C 2 H 3 CN and CH 3 OCH 3 are in the range ∼10 −9 −10 −10 , comparable to those seen in the Orion hot core. In other HMCs Bisschop et al. 2007 found comparable values for C 2 H 5 CN but values ∼2.5 times larger for CH 3 OCH 3 . By comparing the abundance ratio of the pair C 2 H 5 CN/C 2 H 3 CN with the predictions of theoretical models, we derive that the age of our cores ranges between 3.7 and 5.9 × 10 4 yr. Conclusions. The abundances of C 2 H 5 CN and C 2 H 3 CN are strongly correlated, as expected from theory which predicts that C 2 H 3 CN is formed through gas phase reactions involving C 2 H 5 CN . A correlation is also found between the abundances of C 2 H 5 CN and CH 3 OCH 3 , and C 2 H 3 CN and CH 3 OCH 3 . In all tracers the fractional abundances increase with the H 2 column density while they are not correlated with the gas temperature. On average, the chemical and physical differentiation between O-and N-bearing molecules seen in Orion and W3(H 2 O) is not revealed by our observations. We believe that this is partly due to the poor angular resolution of our data, which allows us to derive only average values over the sources of the discussed parameters.

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Section: Introductionmentioning

confidence: 99%

Comparative study of complex N- and O-bearing molecules in hot molecular cores

Fontani

Pascucci

Caselli

et al. 2007

A&A

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“…The hot core associated with G34.26+0.16 has been the target of chemical surveys using single-dish telescopes (MacDonald et al 1996;Hatchell et al 1998) in which complex molecules characteristic of hot cores were detected. Molecular line observations suggest that the hot core does not coincide with the H ii region component C; it is offset to the east by at least 2 ′′ and shows no sign of being internally heated (Heaton et al 1989;MacDonald et al 1995;Watt & Mundy 1999). Based on narrow-band mid-infrared imaging of the complex, Campbell et al (2000) concluded that the same star is responsible for the ionization of the H ii component C and heating the dust but is not interacting with the hot core seen in molecular emission.…”

Section: Introductionmentioning

confidence: 99%

Kinematics and Chemistry of the Hot Molecular Core in G34.26+0.15 at High Resolution

Mookerjea

Casper

Mundy

et al. 2007

ApJ

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We present high angular resolution ($1 00 ) multitracer spectral line observations toward the hot molecular core (HMC) associated with G34.26+0.15 between 87 and 109 GHz. We have mapped emission from (1) complex nitrogenand oxygen-rich molecules such as CH 3 OH, HC 3 N, CH 3 CH 2 CN, NH 2 CHO, CH 3 OCH 3 , and HCOOCH 3 ; (2) sulfurbearing molecules such as OCS, SO, and SO 2 ; and (3) the recombination line H53 . At this high resolution (0.018 pc) we find no evidence for the HMC being internally heated. The continuum peak detected at k ¼ 2:8 mm is consistent with the free-free emission from component C of the ultracompact H ii region, which primarily energizes the HMC. Emissions from the N-and O-bearing molecules peak at different positions within the core; none is coincident with the continuum peak. Lack of high-resolution complementary data sets makes it difficult to decipher whether the different peaks correspond to separate hot cores not resolved by the present data, or whether they are manifestations of the temperature and density structure within a single core. Using brightness temperatures of the optically thick lines in our sample, we estimate the kinetic temperature of the inner regions of the HMC to be 160 AE 30 K. Observed abundances of the different chemical species are not consistently reproduced by the existing hot-core models. There are uncertainties due to (1) unavailability of temperature and density distribution within the hot core, (2) the assumption of a centrally peaked temperature distribution by the chemical models, which is not applicable to externally heated hot cores such as G34.26+0.15, and (3) inadequate knowledge about the formation mechanism of many of the complex molecules.

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“…This large abundance cannot be made by pure gas-phase processes, and they conclude that the ethanol must be formed efficiently in the grain surface chemistry. Macdonald et al (1995) have mapped this object in the J=6-5 CH3CN line using the Nobeyama Millimiter Array and find a compact source coincident with the cores seen in NH3 (3,3). They have have also obtained an IRCAM K-band image with 0.6" resolution which shows emission at 2μιη coincident with that seen in NH3 (3,3).…”

Section: G343+015mentioning

confidence: 97%

Observations of “Hot Cores”

Ohishi

1997

Symp. - Int. Astron. Union

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Abstract. Recent observational results toward the "Hot Core" sources (Orion KL, SgrB2, G34.3+0.15, W51, and so on) are summarized. Several saturated organic molecules are commonly observed among these sources, and these results favor formations on the grain mantles followed by evaporation. Some results of surveys in "hot core molecules" are presented. Such molecules may be used as diagnostics to establish the presence of "hot core" regions.

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Structure and chemistry in the hot molecular core G34.3+0.15

Cited by 5 publications

References 5 publications

Comparative study of complex N- and O-bearing molecules in hot molecular cores

Comparative study of complex N- and O-bearing molecules in hot molecular cores

Kinematics and Chemistry of the Hot Molecular Core in G34.26+0.15 at High Resolution

Observations of “Hot Cores”

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