ALMA Detection of Vibrationally Excited (v<sub>t</sub> = 1, 2) Acetic Acid toward NGC 6334I

Xue, Ci; Remijan, Anthony J.; Brogan, C. L.; Hunter, T. R.; Herbst, Eric; McGuire, Brett A.

doi:10.3847/1538-4357/ab32e0

Cited by 10 publications

(6 citation statements)

References 33 publications

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“…Spectral cubes of SiO (3-2) and CS (6-5) with 2 km s −1 channels were created from the Band 4 and 7 continuumsubtracted data, respectively. With the exception of the C43-6 Band 4 data (McGuire et al 2018;Xue et al 2019;Ligterink et al 2020), results from these ALMA data sets have not previously been published.…”

Section: Almamentioning

confidence: 99%

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Strong Increase in Mid-Infrared Continuum Emission

Hunter

Brogan

Buizer

et al. 2021

ApJL

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In recent years, dramatic outbursts have been identified toward massive protostars via infrared and millimeter dust continuum and molecular maser emission. The longest lived outburst (>6 yr) persists in NGC 6334 I-MM1, a deeply embedded object with no near-IR counterpart. Using FORCAST and HAWC+ on SOFIA, we have obtained the first mid-IR images of this field since the outburst began. Despite being undetected in pre-outburst ground-based 18 μm images, MM1 is now the brightest region at all three wavelengths (25, 37, and 53 μm), exceeding the UCHII region MM3 (NGC 6334 F). Combining the SOFIA data with ALMA imaging at four wavelengths, we construct a spectral energy distribution of the combination of MM1 and the nearby hot core MM2. The best-fit Robitaille radiative transfer model yields a luminosity of (4.9 ± 0.8) × 104 L ⊙. Accounting for an estimated pre-outburst luminosity ratio MM1:MM2 = 2.1 ± 0.4, the luminosity of MM1 has increased by a factor of 16.3 ± 4.4. The pre-outburst luminosity implies a protostar of mass 6.7 M ⊙, which can produce the ionizing photon rate required to power the pre-outburst HCHII region surrounding the likely outbursting protostar MM1B. The total energy and duration of the outburst exceed the S255IR-NIRS3 outburst by a factor of ≳3, suggesting a different scale of event involving expansion of the protostellar photosphere (to ≳20 R ⊙), thereby supporting a higher accretion rate (≳0.0023 M ⊙ yr−1) and reducing the ionizing photon rate. In the grid of hydrodynamic models of Meyer et al., the combination of outburst luminosity and magnitude (3) places the NGC 6334 I-MM1 event in the region of moderate total accretion (∼0.1–0.3 M ⊙) and hence long duration (∼40–130 yr).

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Section: Almamentioning

confidence: 99%

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Strong Increase in Mid-Infrared Continuum Emission

Hunter

Brogan

Buizer

et al. 2021

ApJL

Self Cite

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“…Toward this source, two distinct regions exhibit spectra typical to hot core regions, designated MM1 and MM2 (Zernickel et al 2012;Brogan et al 2016). This source was the site of the first interstellar detections of methoxymethanol (CH 3 OCH 2 OH) (McGuire et al 2017) and the first two vibrationally excited torsional states of acetic acid (CH 3 COOH) (Xue et al 2019) and has been the target of several investigations of complex molecules (El-Abd et al 2019;Melosso et al 2020). ALMA observations of NGC 6334I at an angular resolution of 0.26 in ALMA Bands 4 and 7 were used to search for transitions of CH 3 CSNH 2 toward this source.…”

Section: Search For Ch 3 Csnh 2 Toward Ngc 6334i With Almamentioning

confidence: 99%

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH₃CSNH₂) in the ISM

Remijan

Xue

Margulès

et al. 2022

A&A

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Context. One of the biggest unsolved mysteries of modern astrochemistry is understanding chemical formation pathways in the interstellar medium (ISM) and circumstellar environments. The detections (or even nondetections) of molecules composed of low-abundance atomic species (such as S, P, Si, and Mg) may help to constrain chemical pathways. Thioacetamide (CH3CSNH2) is the sulfur analog to acetemide (CH3CONH2) and it is a viable candidate to search for in astronomical environments – specifically toward regions where other S-bearing molecules have been found and, if possible, that also contain a detection of CH3CONH2. If detected, it would not only continue to expand the view of molecular complexity in astronomical environments, but also help to better elucidate the possible formation pathways of these types of species in these environments. Aims. Our aim is to expand the frequency range of the measured rotational spectrum of CH3CSNH2 beyond 150 GHz and then to use those measurements to extend the search for this species in the ISM. The new laboratory measurements and expanded search cover more parameter space for determining under what conditions CH3CSNH2 may be detected, leading to possible constraints on the formation of large S-bearing molecules found in the ISM. Methods. The rotational spectrum of CH3CSNH2 was investigated up to 650 GHz. Using the newly refined spectrum of CH3CSNH2, as well as additional spectroscopic data on the chemically related species CH3CONH2, a variety of astronomical sources were searched including data from the following large surveys: Prebiotic Interstellar Molecule Survey conducted with the Green Bank Telescope; Exploring molecular complexity with ALMA conducted with the Atacama Large Millimeter/submillimeter Array; and Astrochemical Surveys at IRAM conducted with the Institut de Radioastronomie Millimétrique 30 m Telescope. Results. A total of 1428 transitions from the vt = 0 state with maximum values J = 47 and Ka = 20 in the range up to 330 GHz, and J = 95 and Ka = 20 in the range from 400–660 GHz were assigned. We also assigned 321 transitions from the vt = 1 state with the maximum values J = 35 and Ka = 9 up to 330 GHz. We achieved a final fit with a root-mean-square deviation of 43.4 kHz that contains 2035 measured lines from our study and the literature for vt = 0 and vt = 1 states of A and E symmetries. The final fit is based on the rho-axis-method Hamiltonian model that includes 40 parameters. An astronomical search for CH3CSNH2 was conducted based on all the new spectroscopic data. No transitions of CH3CSNH2 were detected toward any of the sources contained in our survey. Using the appropriate telescope and physical parameters for each astronomical source, upper limits to the column densities were found for CH3CSNH2 toward each source.

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Section: Search For Ch 3 Csnh 2 Toward Ngc 6334i With Almamentioning

confidence: 99%

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH3CSNH2) in the ISM

Remijan,

Xue,

Margulès

et al. 2021

Preprint

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Context. One of the biggest unsolved mysteries of modern astrochemistry is understanding chemical formation pathways in the interstellar medium (ISM) and circumstellar environments (CSEs). The detections (or even nondetections) of molecules composed of low-abundance atomic species (such as S, P, Si, and Mg) may help to constrain chemical pathways. Thioacetamide (CH 3 CSNH 2 ) is the sulfur analog to acetemide (CH 3 CONH 2 ) and it is a viable candidate to search for in astronomical environments -specifically toward regions where other S-bearing molecules have been found and, if possible, that also contain a detection of CH 3 CONH 2 . If detected, it would not only continue to expand the view of molecular complexity in astronomical environments, but also help to better elucidate the possible formation pathways of these types of species in these environments. Aims. Our aim is to expand the frequency range of the measured rotational spectrum of CH 3 CSNH 2 beyond 150 GHz and then to use those measurements to extend the search for this species in the ISM. The new laboratory measurements and expanded search cover more parameter space for determining under what conditions CH 3 CSNH 2 may be detected, leading to possible constraints on the formation of large S-bearing molecules found in the ISM. Methods. The rotational spectrum of CH 3 CSNH 2 was investigated up to 650 GHz. Using the newly refined spectrum of CH 3 CSNH 2 , as well as additional spectroscopic data on the chemically related species CH 3 CONH 2 , a variety of astronomical sources were searched including data from the following large surveys: Prebiotic Interstellar Molecule Survey (PRIMOS) conducted with the Green Bank Telescope (GBT); Exploring molecular complexity with ALMA (EMoCA) conducted with the Atacama Large Millimeter/submillimeter Array (ALMA); and Astrochemical Surveys At IRAM (ASAI) conducted with the Institut de Radioastronomie Millimétrique (IRAM) 30m Telescope. Results. A total of 1428 transitions from the v t =0 state with maximum values J=47 and K a =20 in the range up to 330 GHz, and J=95 and K a =20 in the range from 400-660 GHz were assigned. We also assigned 321 transitions from the v t =1 state with the maximum values J=35 and K a =9 up to 330 GHz. We achieved a final fit with a root-mean-square deviation of 43.4 kHz that contains 2035 measured lines from our study and the literature for v t =0 and v t =1 states of A and E symmetries. The final fit is based on the rho-axismethod (RAM) Hamiltonian model that includes 40 parameters. An astronomical search for CH 3 CSNH 2 was conducted based on all the new spectroscopic data. No transitions of CH 3 CSNH 2 were detected toward any of the sources contained in our survey. Using the appropriate telescope and physical parameters for each astronomical source, upper limits to the column densities were found for CH 3 CSNH 2 toward each source.

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ALMA Detection of Vibrationally Excited (v_t = 1, 2) Acetic Acid toward NGC 6334I

Cited by 10 publications

References 33 publications

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Strong Increase in Mid-Infrared Continuum Emission

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Strong Increase in Mid-Infrared Continuum Emission

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH₃CSNH₂) in the ISM

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH3CSNH2) in the ISM

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ALMA Detection of Vibrationally Excited (vt = 1, 2) Acetic Acid toward NGC 6334I

Cited by 10 publications

References 33 publications

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Strong Increase in Mid-Infrared Continuum Emission

The Extraordinary Outburst in the Massive Protostellar System NGC 6334 I-MM1: Strong Increase in Mid-Infrared Continuum Emission

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH3CSNH2) in the ISM

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH3CSNH2) in the ISM

Contact Info

Product

Resources

About

ALMA Detection of Vibrationally Excited (v_t = 1, 2) Acetic Acid toward NGC 6334I

Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH₃CSNH₂) in the ISM