arXiv subjects

Michael G. Burton

Publications and source records attributed to Michael G. Burton.

At least 19 recordsLinked to original sources

arXiv2026

MAJORS II: HCO+& HCN Abundances in W40

We present observations of HCN and HCO$^+$ J = $3 - 2$ in the central $424'' \times 424''$ region of the W40 massive star forming region. The observations were taken as part of a pilot project for the MAJORS large program at the JCMT telescope. By incorporating prior knowledge of N(H$_2$) and $T_K$, assuming a constant density, and using the RADEX radiative transfer code we found that the HCN and HCO$^+$ abundances range from $X$(HCN) = $0.4-7.0 \times 10^{-8}$ and $X$(HCO$^+$) = $0.4-7.3 \times 10^{-9}$. Additional modelling using the NAUTILUS chemical evolution code, that takes H$_2$ density variations into account, however, suggests the HCN and HCO$^+$ abundances may be fairly constant. Careful modelling of three different positions finds $X$(HCN) = $1.3-1.7 \times 10^{-8}$, $X$(HCO$^+$) = $1.3-3.1 \times 10^{-9}$. Cross-comparison of the two models also provides a crude estimate of the gas density producing the HCN and HCO$^+$ emission, with H$_2$ densities in the range $5 \times 10^4 - 5 \times 10^5$ cm$^{-3}$, suggesting that the HCN and HCO$^+$ emission does indeed arise from dense gas. High UV intensity (e.g. $G_o >$ a few thousand) has no effect on the abundances in regions where the visual extinction is large enough to effectively shield the gas from the UV field. In regions where $A_V < 6$, however, the abundance of both species is lowered due to destructive reactions with species that are directly affected by the radiation field.

astro-ph.GA↗

arXiv2025

Photometric Mapping of Carbonaceous/Siliceous Dust and Water Ice in the ISM with JWST: Applications to the Dense Sightlines

We introduce a new photometric mapping method for the James Webb Space Telescope (JWST) to measure the spatial distribution of carbonaceous dust, siliceous dust and water ice by using absorption features arising from the grains in the dense interstellar medium (ISM). Employing NIRCam and MIRI imaging filters, low-resolution spectroscopic data can be obtained to measure the optical depths of the 3.0-$μ$m water ice -OH feature, the 3.4-$μ$m aliphatic hydrocarbon -CH feature, and the 10-$μ$m silicate -SiO feature for large fields of view. This method provides extensive statistical data of the grains across wide fields in the ISM at minimal observing cost. In this study, we present its application on observational data from the literature to validate the measured optical depths and simulations to assess the accuracy of the method under various conditions. We showed that the photometric method can be employed to obtain reasonably accurate measurements of optical depth. We demonstrate that JWST optical depth maps enable the independent exploration of abundance distributions of major grain components across a wide spatial coverage in the ISM.

astro-ph.IM↗

arXiv2023

Analysis of the first infrared spectrum of quasi-bound H2 line emission in Herbig-Haro 7

Context. Highly excited molecular hydrogen H2 has been observed in many regions of shocked molecular gas. A recently published $K$-band spectrum of Herbig-Haro 7 (HH7) contains several vibration-rotation lines of H2 from highly excited energy levels that have not been detected elsewhere, including a line at 2.179 $μ$m identified as arising from the $v$=2 $J$=29 level, which lies above the dissociation limit of H2. One emission line at 2.104 $μ$m in this spectrum was unidentified. Aims. We aim to complete the analysis of the spectrum of HH7 by including previously missing molecular data that have been recently computed. Methods. We re-analysed the $K$-band spectrum, emphasising the physics of quasi-bound upper levels that can produce infrared emission lines in the $K$ band. Results. We confirm the identification of the $2-1$ $S$(27) line at 2.1785 $μ$m and identify the line at 2.1042 $μ$m as due to the 1-0 $S$(29) transition of H2, whose upper level energy is also higher than the dissociation limit. This latter identification, its column density, and the energy of its upper level further substantiate the existence of a hot thermal component at 5000 K in the HH7 environment.} Conclusion. The presence of the newly identified $1-0$ $S$(29) line, whose quasi-bound upper level ($v$=1, $J$=31) has a significant spontaneous dissociation probability, shows that dissociation of H2 is occurring. The mechanism by which virtually all of the H2 levels with energies from 20,000 K to 53,000 K is maintained in local thermodynamic equilibrium at a single temperature of $\sim$5,000 K remains to be understood.

astro-ph.GA↗

arXiv2020

The Carina Nebula and Gum 31 molecular complex III: The distribution of the 1-3 GHz radio continuum across the whole nebula

We report the most detailed $1-3$ GHz radio continuum emission map of the nearest region of massive star formation, the Carina Nebula. As part of a large program with the Australia Telescope Compact Array, we have covered $\sim$ 12 deg$^2$, achieving an angular resolution of $\sim$ 16 arcsec, representing the largest and most complete map of the radio continuum to date. Our continuum map shows a spectacular and complex distribution of emission across the nebula, with multiple structures such as filaments, shells, and fronts across a wide range of size scales. The ionization fronts have advanced far into the southern and northern region of the Galactic Plane, as fronts are clearly detected at distances $\sim$ 80 pc from the stellar clusters in the center. We estimated an ionization photon luminosity $Q_\mathrm{H}=(7.8 \pm 0.8) \times 10^{50}$ s$^{-1}$ which corresponds to $\sim 85\%$ of the total value obtained from stellar population studies. Thus, approximately $15\%$ of the ionizing flux has escaped from the nebula into the diffuse Galactic Interstellar Medium. Comparison between radio continuum and the hydrogen atomic and molecular gas maps offers a clear view of the bipolar outflow driven by the energy released by the massive stellar clusters that also affects the fraction of molecular gas across the nebula. Comparison between 8$μ$m and 70$μ$m emission maps and the radio continuum reveals how the hot gas permeates through the molecular cloud, shapes the material into features such as pillars, small shells and arc-like structures, and ultimately, escapes.

astro-ph.GA↗

arXiv2020

Effect of feedback of massive stars in the fragmentation, distribution, and kinematics of the gas in two star forming regions in the Carina Nebula

We present ALMA high spatial resolution observations towards two star forming regions located in one of the most extreme zones of star formation in the Galaxy, the Carina Nebula. One region is located at the center of the nebula and is severally affected by the stellar feedback from high-mass stars, while the other region is located further south and is less disturbed by the massive star clusters. We found that the region at the center of the nebula is forming less but more massive cores than the region located in the south, suggesting that the level of stellar feedback effectively influence the fragmentation process in clumps. Lines such as HCN, HCO$^{+}$ and SiO show abundant and complex gas distributions in both regions, confirming the presence of ionization and shock fronts. Jeans analysis suggests that the observed core masses in the region less affected by the massive stars are consistent with thermal fragmentation, but turbulent Jeans fragmentation might explain the high masses of the cores identified in the region in the center of Carina. Consistently, two different analyses in the HCO$^{+}$ line provided evidence for a higher level of turbulence in the gas more affected by the stellar feedback. The gas column density probability functions, N-PDFs, show log-normal shapes with clear transitions to power law regimes. We observed a wider N-PDF in the region at the center of the nebula, which provides further evidence for a higher level of turbulence in the material with a higher level of massive stellar feedback.

astro-ph.GA↗

arXiv2019

Probing ISM Structure in Trumpler 14 & Carina I Using The Stratospheric Terahertz Observatory 2

We present observations of the Trumpler 14/Carina I region carried out using the Stratospheric Terahertz Observatory 2 (STO2). The Trumpler 14/Carina I region is in the west part of the Carina Nebula Complex, which is one of the most extreme star-forming regions in the Milky Way. We observed Trumpler 14/Carina I in the 158 $μ$m transition of [C\,{\sc ii}] with a spatial resolution of 48$''$ and a velocity resolution of 0.17 km s$^{-1}$. The observations cover a 0.25$^\circ$ by 0.28$^\circ$ area with central position {\it l} = 297.34$^\circ$, {\it b} = -0.60$^\circ$. The kinematics show that bright [C\,{\sc ii}] structures are spatially and spectrally correlated with the surfaces of CO clouds, tracing the photodissociation region and ionization front of each molecular cloud. Along 7 lines of sight that traverse Tr 14 into the dark ridge to the southwest, we find that the [C\,{\sc ii}] luminosity from the HII region is 3.7 times that from the PDR. In same los we find in the PDRs an average ratio of 1:4.1:5.6 for the mass in atomic gas:dark-CO gas: molecular gas traced by CO. Comparing multiple gas tracers including HI 21cm, [C\,{\sc ii}], CO, and radio recombination lines, we find that the HII regions of the Carina Nebula Complex are well-described as HII regions with one-side freely expanding towards us, consistent with the champagne model of ionized gas evolution. The dispersal of the GMC in this region is dominated by EUV photoevaporation; the dispersal timescale is 20-30 Myr.

astro-ph.GA↗

arXiv2019

Natal molecular cloud of SNR Kes 41. Complete characterisation

Using high-resolution data of the $^{12}$CO and $^{13}$CO ($J$=1-0}) line emission from The Mopra Southern Galactic Plane CO Survey in conjunction with neutral hydrogen observations from the Southern Galactic Plane Survey (SGPS) and mid-infrared Spitzer data, we have explored the large-scale environment of the supernova remnant Kes 41. On the basis of these data, we identified for the first time the parent cloud of Kes 41 in its whole extension and surveyed the HII regions, masers, and the population of massive young stellar objects in the cloud. The whole unveiled giant cloud, located at the kinematic distance of 12.0 $\pm$ 3.6 kpc, whose average total mass and size are $\sim$10-30 $\times10^5$ M$_\odot$ and $\sim$$26^{\prime}$, also shines in $γ$-rays, as revealed by the Large Area Telescope on board the Fermi satellite. We determined a high average proton density $\sim$500-1000~cm$^{-3}$ in the large molecular complex, of which protons from the neutral atomic and ionised gases comprise only $\sim$15%.

astro-ph.HE↗

arXiv2019

Near-infrared [Fe II] and H$_{2}$ Emission-line Study of Galactic Supernova Remnants in the First Quadrant

We report the detection of near-infrared (NIR) [Fe II] (1.644 $μ$m) and H$_{2}$ 1-0 S(1) (2.122 $μ$m) line features associated with Galactic supernova remnants (SNRs) in the first quadrant using two narrowband imaging surveys, UWIFE and UWISH2. Among the total of 79 SNRs fully covered by both surveys, we found 19 [Fe II]-emitting and 19 H$_{2}$-emitting SNRs, giving a detection rate of 24% for each. Eleven SNRs show both emission features. The detection rate of [Fe II] and H$_{2}$ peaks at the Galactic longitude ($l$) of $40^{\circ}$-$50^{\circ}$ and $30^{\circ}$-$40^{\circ}$, respectively, and gradually decreases toward smaller/larger $l$. Five out of the eleven SNRs emitting both emission lines clearly show an "[Fe II]-H$_{2}$ reversal," where H$_{2}$ emission features are found outside the SNR boundary in [Fe II] emission. Our NIR spectroscopy shows that the H$_{2}$ emission originates from collisionally excited H$_{2}$ gas. The brightest SNR in both [Fe II] and H$_{2}$ emissions is W49B, contributing more than 70% and 50% of the total [Fe II] 1.644 $μ$m ($2.0 \times 10^4$ L$_{\odot}$) and H$_{2}$ 2.122 $μ$m ($1.2 \times 10^3$ L$_{\odot}$) luminosities of the detected SNRs. The total [Fe II] 1.644 $μ$m luminosity of our Galaxy is a few times smaller than that expected from the SN rate using the correlation found in nearby starburst galaxies. We discuss possible explanations for this.

astro-ph.GA↗

arXiv2019

The G332 molecular cloud ring: I. Morphology and physical characteristics

We present a morphological and physical analysis of a Giant Molecular Cloud (GMC) using the carbon monoxide isotopologues ($^{12}$CO, $^{13}$CO, C$^{18}$O $^{3}P_{2}\rightarrow$ $^{3}P_{1}$) survey of the Galactic Plane (Mopra CO Southern Galactic Plane Survey), supplemented with neutral carbon maps from the HEAT telescope in Antarctica. The giant molecular cloud structure (hereinafter the ring) covers the sky region $332^\circ$ < $\ell$ < $333^\circ$ and $\mathit{b}$ = $\pm 0.5^\circ$ (hereinafter the G332 region). The mass of the ring and its distance are determined to be respectively ~2$\times10^{5}\mathrm{M_{\odot}}$ and ~3.7 kpc from Sun. The dark molecular gas fraction, estimated from the $^{13}$CO and [CI] lines, is $\sim17\%$ for a CO T$_{\mathrm{ex}}$ between [10,20 K]. Comparing the [CI] integrated intensity and N(H$_{2}$) traced by $^{13}$CO and $^{12}$CO, we define an X$\mathrm{_{CI}^{809}}$ factor, analogous to the usual X$_{\mathrm{co}}$, through the [CI] line. X$\mathrm{_{CI}^{809}}$ ranges between [1.8,2.0]$\times10^{21}\mathrm{cm}^{-2}\mathrm{K}^{-1}\mathrm{km}^{-1}\mathrm{s}$. We examined local variation in X$_{\mathrm{co}}$ and T$_{\mathrm{ex}}$ across the cloud, and find in regions where the star formation activity is not in an advanced state, an increase in the mean and dispersion of the X$_{\mathrm{co}}$ factor as the excitation temperature decreases. We present a catalogue of C$^{18}$O clumps within the cloud. The star formation (SF) activity ongoing in the cloud shows a correlation with T$_{\mathrm{ex}}$, [CI] and CO emissions, and anti-correlation with X$_{\mathrm{co}}$, suggesting a North-South spatial gradient in the SF activity. We propose a method to disentangle dust emission across the Galaxy, using HI and $^{13}$CO data. We describe Virtual Reality (VR) and Augmented Reality (AR) data visualisation techniques for the analysis of radio astronomy data.

astro-ph.GA↗

arXiv2018

Environmental conditions shaping star formation: The Carina Nebula

Using the Mopra telescope, we have targeted 61 regions in the Carina Nebula, covering an area of 1.5 square degrees, of bright and compact 870 $μ$m dust continuum emission for molecular line emission from a host of 16 spectral lines at 3mm, including several dense gas tracers. We found that the clumps detected in Carina in general have in average higher temperatures (27 K compared to 21 K), and lower masses (214 M$_\odot$ compared to 508 M$_\odot$) than clumps located at a similar distance to us in the Galactic Plane. We compare the properties of the molecular line emission of these clumps with the MALT90 survey, finding that the detection rates of the molecular lines are similar to MALT90 clumps that are classified as PDRs. However, most of the clumps located within 10' of $η$ Carina have little molecular line emission detected in our observations. Given the lack of maser detection in the Carina region, we also compared the properties the clumps in Carina to those of Galactic clumps associated with 6.7-GHz methanol masers. We found that the clumps in Carina are warmer, less massive, and show less emission from the four most commonly detected molecules, HCO$^+$, N$_2$H$^+$, HCN, and HNC, compared to clumps associated with masers in the Galactic Plane. Overall our results are consistent with the scenario in which the high radiation field of $η$ Carina is dramatically affecting its local environment, and therefore the chemical composition of the dense clumps.

astro-ph.GA↗

arXiv2018

A revisited study of the unidentified $γ$-ray emission towards the SNR Kes 41

Kes 41 is among the Galactic supernova remnants (SNRs) proposed to be physically linked to $γ$-ray emission at GeV energies. Although not conclusively, the nature of the $γ$-ray photons has been explained by means of hadronic collisions of particles accelerated at the SNR blast wave with target protons in an adjacent molecular clump. We performed an analysis of Fermi-Large Area Telescope (LAT) data of about 9 years to assess the origin of the $γ$-ray emission. To investigate this matter we also used spectral modelling constraints from the physical properties of the interstellar medium towards the $γ$-ray emitting region along with a revised radio continuum spectrum of Kes 41 ($α= -0.54 \pm 0.10$, $S\proptoν^α$). We demonstrated that the $γ$-ray fluxes in the GeV range can be explained through bremsstrahlung emission from electrons interacting with the surrounding medium. We also consider a model in which the emission is produced by pion-decay after hadronic collisions, and confirmed that this mechanism cannot be excluded.

astro-ph.HE↗

arXiv2018

RCW 36 in the Vela Molecular Ridge: Evidence for a high-mass star cluster formation triggered by Cloud-Cloud Collision

A collision between two molecular clouds is one possible candidate for high-mass star formation. The HII region RCW 36, located in the Vela molecular ridge, contains a young star cluster with two O-type stars. We present new CO observations of RCW 36 with NANTEN2, Mopra, and ASTE using $^{12}$CO($J$ = 1-0, 2-1, 3-2) and $^{13}$CO($J$ = 2-1) line emissions. We have discovered two molecular clouds lying at the velocities $V_\mathrm{LSR} \sim$5.5 and 9 km s$^{-1}$. Both clouds are likely to be physically associated with the star cluster, as verified by the good spatial correspondence among the two clouds, infrared filaments, and the star cluster. We also found a high intensity ratio of $\sim$0.6-1.2 for CO $J$ = 3-2 / 1-0 toward both clouds, indicating that the gas temperature has been increased due to heating by the O-type stars. We propose that the O-type stars in RCW 36 were formed by a collision between the two clouds, with a relative velocity separation of 5 km s$^{-1}$. The complementary spatial distributions and the velocity separation of the two clouds are in good agreement with observational signatures expected for O-type star formation triggered by a cloud-cloud collision. We also found a displacement between the complementary spatial distributions of the two clouds, which we estimate to be 0.3 pc assuming the collision angle to be 45$^{\circ}$ relative to the line-of-sight. We estimate the collision timescale to be $\sim$10$^5$ yr. It is probable that the cluster age by Ellerbroek et al. (2013b) is dominated by the low-mass members which were not formed under the triggering by cloud-cloud collision, and that the O-type stars in the center of the cluster are explained by the collisional triggering independently from the low-mass star formation.

astro-ph.GA↗

arXiv2017

Near-Infrared Knots and Dense Fe Ejecta in the Cassiopeia A Supernova Remnant

We report the results of broadband (0.95--2.46 $μ$m) near-infrared spectroscopic observations of the Cassiopeia A supernova remnant. Using a clump-finding algorithm in two-dimensional dispersed images, we identify 63 "knots" from eight slit positions and derive their spectroscopic properties. All of the knots emit [Fe II] lines together with other ionic forbidden lines of heavy elements, and some of them also emit H and He lines. We identify 46 emission line features in total from the 63 knots and measure their fluxes and radial velocities. The results of our analyses of the emission line features based on principal component analysis show that the knots can be classified into three groups: (1) He-rich, (2) S-rich, and (3) Fe-rich knots. The He-rich knots have relatively small, $\lesssim 200~{\rm km~s}^{-1}$, line-of-sight speeds and radiate strong He I and [Fe II] lines resembling closely optical quasi-stationary flocculi of circumstellar medium, while the S-rich knots show strong lines from O-burning material with large radial velocities up to $\sim 2000~{\rm km~s}^{-1}$ indicating that they are supernova ejecta material known as fast-moving knots. The Fe-rich knots also have large radial velocities but show no lines from O-burning material. We discuss the origin of the Fe-rich knots and conclude that they are most likely "pure" Fe ejecta synthesized in the innermost region during the supernova explosion. The comparison of [Fe II] images with other waveband images shows that these dense Fe ejecta are mainly distributed along the southwestern shell just outside the unshocked $^{44}$Ti in the interior, supporting the presence of unshocked Fe associated with $^{44}$Ti.

astro-ph.GA↗

arXiv2015

Extended Carbon Line Emission in the Galaxy: Searching for Dark Molecular Gas along the G328 Sightline

We present spectral data cubes of the [CI] 809GHz, 12CO 115GHz, 13CO 110GHz and HI 1.4GHz line emission from an 1 square degree region along the l = 328° (G328) sightline in the Galactic Plane. Emission arises principally from gas in three spiral arm crossings along the sight line. The distribution of the emission in the CO and [CI] lines is found to be similar, with the [CI] slightly more extended, and both are enveloped in extensive HI. Spectral line ratios per voxel in the data cubes are found to be similar across the entire extent of the Galaxy. However, towards the edges of the molecular clouds the [CI]/13CO and 12CO/13CO line ratios rise by ~50%, and the [CI]/HI ratio falls by ~10$%. We attribute this to these sightlines passing predominantly through the surfaces of photodissociation regions (PDRs), where the carbon is found mainly as C or C+, while the H2 is mostly molecular, and the proportion of atomic gas also increases. We undertake modelling of the PDR emission from low density molecular clouds excited by average interstellar radiation fields and cosmic-ray ionization to quantify this comparison, finding that depletion of sulfur and reduced PAH abundance is needed to match line fluxes and ratios. Roughly one-third of the molecular gas along the sightline is found to be associated with this surface region, where the carbon is largely not to be found in CO. ~10% of the atomic hydrogen along the sightline is cold gas within PDRs.

astro-ph.GA↗

arXiv2015

Lord of the Rings: A Kinematic Distance to Circinus X-1 from a Giant X-Ray Light Echo

Circinus X-1 exhibited a bright X-ray flare in late 2013. Follow-up observations with Chandra and XMM-Newton from 40 to 80 days after the flare reveal a bright X-ray light echo in the form of four well-defined rings with radii from 5 to 13 arcminutes, growing in radius with time. The large fluence of the flare and the large column density of interstellar dust towards Circinus X-1 make this the largest and brightest set of rings from an X-ray light echo observed to date. By deconvolving the radial intensity profile of the echo with the MAXI X-ray lightcurve of the flare we reconstruct the dust distribution towards Circinus X-1 into four distinct dust concentrations. By comparing the peak in scattering intensity with the peak intensity in CO maps of molecular clouds from the Mopra Southern Galactic Plane CO Survey we identify the two innermost rings with clouds at radial velocity ~ -74 km/s and ~ -81 km/s, respectively. We identify a prominent band of foreground photoelectric absorption with a lane of CO gas at ~ -32 km/s. From the association of the rings with individual CO clouds we determine the kinematic distance to Circinus X-1 to be $D_{Cir X-1} = 9.4^{+0.8}_{-1.0}$ kpc. This distance rules out earlier claims of a distance around 4 kpc, implies that Circinus X-1 is a frequent super-Eddington source, and places a lower limit of $Γ\gtrsim 22$ on the Lorentz factor and an upper limit of $θ_{jet} \lesssim 3^{\circ}$ on the jet viewing angle.

astro-ph.HE↗

arXiv2015

The Mopra Southern Galactic Plane CO Survey - Data Release 1

We present observations of the first ten degrees of longitude in the Mopra carbon monoxide (CO) survey of the southern Galactic plane (Burton et al. 2013), covering Galactic longitude l = 320-330° and latitude b = $\pm$0.5°, and l = 327-330°, b = +0.5-1.0°. These data have been taken at 35 arc sec spatial resolution and 0.1 km/s spectral resolution, providing an unprecedented view of the molecular clouds and gas of the southern Galactic plane in the 109-115 GHz J = 1-0 transitions of 12CO, 13CO, C18O and C17O. Together with information about the noise statistics from the Mopra telescope, these data can be retrieved from the Mopra CO website and the CSIRO-ATNF data archive.

astro-ph.GA↗

arXiv2015

MALT-45: A 7 mm survey of the southern Galaxy - I. Techniques and spectral line data

We present the first results from the MALT-45 (Millimetre Astronomer's Legacy Team - 45 GHz) Galactic Plane survey. We have observed 5 square-degrees ($l = 330 - 335$, $b = \pm0.5$) for spectral lines in the 7 mm band (42-44 and 48-49 GHz), including $\text{CS}$ $(1-0)$, class I $\text{CH}_3\text{OH}$ masers in the $7(0,7)-6(1,6)$ $\text{A}^{+}$ transition and $\text{SiO}$ $(1-0)$ $v=0,1,2,3$. MALT-45 is the first unbiased, large-scale, sensitive spectral line survey in this frequency range. In this paper, we present data from the survey as well as a few intriguing results; rigorous analyses of these science cases are reserved for future publications. Across the survey region, we detected 77 class I $\text{CH}_3\text{OH}$ masers, of which 58 are new detections, along with many sites of thermal and maser $\text{SiO}$ emission and thermal $\text{CS}$. We found that 35 class I $\text{CH}_3\text{OH}$ masers were associated with the published locations of class II $\text{CH}_3\text{OH}$, $\text{H}_2\text{O}$ and $\text{OH}$ masers but 42 have no known masers within 60 arcsec. We compared the MALT-45 $\text{CS}$ with $\text{NH}_3$ (1,1) to reveal regions of $\text{CS}$ depletion and high opacity, as well as evolved star-forming regions with a high ratio of $\text{CS}$ to $\text{NH}_3$. All $\text{SiO}$ masers are new detections, and appear to be associated with evolved stars from the $\it{Spitzer}$ Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). Generally, within $\text{SiO}$ regions of multiple vibrational modes, the intensity decreases as $v=1,2,3$, but there are a few exceptions where $v=2$ is stronger than $v=1$.

astro-ph.SR↗

arXiv2014

New detections of HC$_{5}$N toward hot cores associated with 6.7 GHz methanol masers

We present new detections of cyanodiacetylene (HC$_{5}$N) toward hot molecular cores, observed with the Tidbinbilla 34 m radio telescope (DSS-34). In a sample of 79 hot molecular cores, HC$_{5}$N was detected towards 35. These results are counter to the expectation that long chain cyanopolyynes, such as HC$_{5}$N, are not typically found in hot molecular cores, unlike their shorter chain counterpart HC$_{3}$N. However it is consistent with recent models which suggest HC$_{5}$N may exist for a limited period during the evolution of hot molecular cores.

astro-ph.GA↗