Mcguire Apjs 2018.Pdf

The Astrophysical Journal Supplement Series, 239:17 (48pp), 2018 December https://doi.org/10.3847/1538-4365/aae5d2 © 2018. The American Astronomical Society. 2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules Brett A. McGuire1,2,3 1 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA 2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA Received 2018 May 27; revised 2018 September 20; accepted 2018 September 20; published 2018 November 26 Abstract To date, 204 individual molecular species, comprised of 16 different elements, have been detected in the interstellar and circumstellar medium by astronomical observations. These molecules range in size from 2 atoms to 70, and have been detected across the electromagnetic spectrum from centimeter wavelengths to the ultraviolet. This census presents a summary of the first detection of each molecular species, including the observational facility, wavelength range, transitions, and enabling laboratory spectroscopic work, as well as listing tentative and disputed detections. Tables of molecules detected in interstellar ices, external galaxies, protoplanetary disks, and exoplanetary atmospheres are provided. A number of visual representations of these aggregate data are presented and briefly discussed in context. Key words: astrochemistry – ISM: molecules Supporting material: tar.gz file 1. Introduction Tielens 2008), or at the very least sp2-hybridized aromatic carbon structures. The possibility that these features arise from Since the detection of methylidyne (CH), the first molecule mixed aromatic/aliphatic organic nanoparticles has also been identified in the interstellar medium (ISM; Swings & raised (Kwok & Zhang 2013). Regardless, it remains that no Rosenfeld 1937; Dunham 1937; McKellar 1940), observations individual molecule has been definitely identified from UIR of molecules have played crucial roles in a wide range of features. applications, from broadening our understanding of interstellar An older mystery is the diffuse interstellar bands (DIBs), first chemical evolution (Herbst & van Dishoeck 2009) and the discovered by Mary Lea Heger in 1922 (McCall & Griffin formation of planets (Öberg et al. 2011), to providing 2012). Despite nearly a century of observation and laboratory exceptional astrophysical probes of physical conditions and work, these sharp features seen from the IR to the UV remain processes (Friesen et al. 2013). Beginning in the early 1960s, nearly completely unassigned. Campbell et al. (2015) recently the advent of radio astronomy enabled a boom in the detection reported the first attribution of a molecular carrier to a DIB that of new molecules, a trend that has continued at a nearly linear + has not been disputed in the literature, that of C60 . Yet, rate ever since. fi Yet, despite the remarkably steady (and perhaps even hundreds of DIBs remain to be identi ed. In the following sections, known, tentatively detected, and accelerating) pace of new molecular detections, the number disputed interstellar, circumstellar, extragalactic, and exopla- of as yet unidentified spectral features attributable to molecules netary molecules are cataloged and presented. The major lists is staggering. Indeed, these mysteries extend across the in this paper are as follows (names are in-document hyperlinks electromagnetic spectrum. In the radio, high-sensitivity, broad- ) band spectral line surveys continue to reveal hundreds of in most PDF viewers : features not assignable to transitions of molecules in spectro- 1. List of known interstellar and circumstellar molecules scopic databases (Cernicharo et al. 2013a), although there is (a) List of tentative detections. evidence that a non-trivial number of these features may be due (b) List of disputed detections. to transitions of vibrationally excited or rare isotopic species 2. List of molecules detected in external galaxies. that have not been completely cataloged (Fortman et al. 2012). 3. List of molecules detected in interstellar ices. At shorter wavelengths, the unidentified infrared emission 4. List of molecules detected in protoplanetary disks. bands (UIRs)—sharp, distinct emission features ubiquitous in The primary list is that of the known interstellar and ultraviolet (UV)-irradiated regions in our galaxy, as well as circumstellar molecules, and for each species in this list, a best- seen in dozens of external galaxies—continue to elude effort attempt was made to locate the first reported detection or conclusive molecular identification. A substantial body of detections of the species in the literature. The detection source or literature now seems to favor the assignment of these emission sources and instrument are given, and for some species a short features to polyclic aromatic hydrocarbons (PAHs; description of any particularly noteworthy attributes is given as 3 well. When available, a reference to the enabling laboratory B.A.M. is a Hubble Fellow of the National Radio Astronomy Observatory. spectroscopy work cited in the detection paper is provided. In the cases where the detection paper uses frequencies without apparent Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further attribution to the laboratory spectroscopy, the most recent effort in distribution of this work must maintain attribution to the author(s) and the title the literature that would reasonably have been available at the time of the work, journal citation and DOI. of publication of the detection is provided on a best-effort basis. 1 The Astrophysical Journal Supplement Series, 239:17 (48pp), 2018 December McGuire Table 1 known interstellar and circumstellar molecules. The column Commonly Used Facility Abbreviations headers and individual molecule entries are active in-document Abbreviation Description hyperlinks in most PDF viewers. In Section 10, an aggregate analysis of the data is presented. These figures are available / ALMA Atacama Large Millimeter submillimeter Array as high-quality supplemental data files in PDF and PNG fi APEX Atacama Path nder Experiment formats. ARO Arizona Radio Observatory ATCA Australian Telescope Compact Array BIMA Berkeley-Illinois-Maryland Array 2. Detection Techniques CSO Caltech Submillimeter Observatory As will be seen in the following pages, the vast majority of FCRAO Five College Radio Astronomy Observatory new molecule detections (∼80%) have been made using radio FUSE Far Ultraviolet Spectroscopic Explorer astronomy techniques in the centimer, millimeter, and GBT Green Bank Telescope submillimeter wavelength ranges. This article, and indeed this IRAM Institut de Radioastronomie Millimétrique IRTF Infrared Radio Telescope Facility section, is therefore inherently biased toward radio astronomy. ISO Infrared Space Observatory To understand this bias, it is helpful to review the techniques, KPNO Kitt Peak National Observatory and their limitations, used to detect molecules across various MWO Millimeter-wave Observatory wavelength ranges. In the end, it comes down to the energy NRAO National Radio Astronomy Observatory required, and that which is available, to populate molecular OVRO Owens Valley Radio Observatory energy levels for undergoing transitions at various wave- PdBI Plateau de Bure Interferometer lengths. This in turn dictates the environments and sightlines in SEST Swedish-ESO Submillimeter Telescope which detections can be accomplished. SMA Sub-millimeter Array SMT Sub-millimeter Telescope 2.1. Radio Astronomy SOFIA Stratospheric Observatory for Infrared Astronomy UKIRT United Kingdom Infrared Telescope Here, radioastronomical observations are roughly defined as those stretching from centimeter to far-infrared (100ʼsofμm) wavelengths, or below ∼2THz (in frequency). The primary The classification of a molecule as detected, tentatively molecular signal arising in these regions is that of the rotational detected, or disputed was made as agnostically as possible. motion of molecules. For a linear molecule (symmetric and Molecules are listed as detected if a literature source has asymmetric tops follow similar, if more complex patterns), the claimed that detection, did not self-identify that detection as rotational energy levels J are given, to first order, by tentative, and no subsequent literature could be found that Equation (1): disputes that claim. Tentative detections are listed only if the EBJJ=+ source has claimed the detection as such. Detections are J ()1, () 1 considered disputed until a literature source has claimed that where B is the rotational constant of the molecule. B is inversely dispute has been resolved. proportional to the moment of inertia of the molecule (I): Subsets of the lists presented in this work are available both online and in numerous publications. Three exceptional web- h2 based resources are of particular note with respect to the list of B = ,2() interstellar and circumstellar detections: the Cologne Database 8p2I for Molecular Spectroscopy’s List of Molecules in Space (H.S.P. 4 Müller), The Astrochymist’s A Bibliography of Astromolecules where I is related to the reduced mass of the molecule (μ) and 5 6 (D. Woon), and the list of M. Araki. At the time of publication, the radial extent of the mass (r): these resources provide the most frequently updated lists of known interstellar and circumstellar species. This publication is Ir= m 2.3() intended as a complement, rather than a supplement, to these resources. Thus, lighter, smaller molecules

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