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14 results on '"Thomas S.-Y. Lai"'

1. GOALS-JWST: The Warm Molecular Outflows of the Merging Starburst Galaxy NGC 3256

Author

Thomas Bohn, Hanae Inami, Aditya Togi, Lee Armus, Thomas S.-Y. Lai, Loreto Barcos-Munoz, Yiqing Song, S. T. Linden, Jason Surace, Marina Bianchin, Vivian U, Aaron S. Evans, Torsten Böker, Matthew A. Malkan, Kirsten L. Larson, Sabrina Stierwalt, Victorine A. Buiten, Vassilis Charmandaris, Tanio Diaz-Santos, Justin H. Howell, George C. Privon, Claudio Ricci, Paul P. van der Werf, Susanne Aalto, Christopher C. Hayward, Justin A. Kader, Joseph M. Mazzarella, Francisco Muller-Sanchez, and David B. Sanders

Subjects
Galaxy mergers, Infrared astronomy, Infrared sources, Luminous infrared galaxies, Molecular gas, Galaxy winds, Astrophysics, QB460-466
Abstract

We present James Webb Space Telescope (JWST) integral-field spectrograph observations of NGC 3256, a local infrared-luminous late-stage merging system with two nuclei roughly 1 kpc apart, both of which have evidence of cold molecular outflows. Using JWST/NIRSpec and Mid-Infrared Instrument data sets, we investigate this morphologically complex system on spatial scales of

Published
2024
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2. The Metallicity Dependence of PAH Emission in Galaxies. I. Insights from Deep Radial Spitzer Spectroscopy

Author

Cory M. Whitcomb, J.-D. T. Smith, Karin Sandstrom, Carl A. Starkey, Grant P. Donnelly, Bruce T. Draine, Evan D. Skillman, Daniel A. Dale, Lee Armus, Brandon S. Hensley, Thomas S.-Y. Lai, and Robert C. Kennicutt

Subjects
Polycyclic aromatic hydrocarbons, Metallicity, Spiral galaxies, Astrophysics, QB460-466
Abstract

We use deep Spitzer mid-infrared spectroscopic maps of radial strips across three nearby galaxies with well-studied metallicity gradients (M101, NGC 628, and NGC 2403) to explore the physical origins of the observed deficit of polycyclic aromatic hydrocarbons (PAHs) at subsolar metallicity (i.e., the PAH–metallicity relation or PZR). These maps allow us to trace the evolution of all PAH features from 5–18 μ m as metallicity decreases continuously from solar ( Z _⊙ ) to 0.2 Z _⊙ . The total PAH-to-dust luminosity ratio remains relatively constant until reaching a threshold of ∼ 2/3 Z _⊙ , below which it declines smoothly but rapidly. The PZR has been attributed to preferential destruction of the smallest grains in the hard radiation environments found at low metallicity. In this scenario, a decrease in emission from the shortest-wavelength PAH features is expected. In contrast, we find a steep decline in long-wavelength power below Z _⊙ , especially in the 17 μ m feature, with the shorter-wavelength PAH bands carrying an increasingly large fraction of power at low metallicity. We use newly developed grain models to reproduce the observed PZR trends, including these variations in fractional PAH feature strengths. The model that best reproduces the data employs an evolving grain size distribution that shifts to smaller sizes as metallicity declines. We interpret this as a result of inhibited grain growth at low metallicity, suggesting continuous replenishment in the interstellar medium is the dominant process shaping the PAH grain population in galaxies.

Published
2024
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3. Spectroscopic Constraints on the Mid-infrared Attenuation Curve. I. Attenuation Model Using Polycyclic Aromatic Hydrocarbon Emission

Author

Thomas S.-Y. Lai, J. D. T. Smith, Els Peeters, Henrik W. W. Spoon, Shunsuke Baba, Masatoshi Imanishi, and Takao Nakagawa

Subjects
Interstellar dust extinction, Polycyclic aromatic hydrocarbons, Starburst galaxies, Luminous infrared galaxies, Ultraluminous infrared galaxies, Astrophysics, QB460-466
Abstract

We introduce a novel model to spectroscopically constrain the mid-infrared (MIR) extinction/attenuation curve from 3–17 μ m, using polycyclic aromatic hydrocarbon (PAH) emission drawn from an AKARI–Spitzer extragalactic cross-archival data set. Currently proposed MIR extinction curves vary significantly in their slopes toward the near-infrared, and the variation in the strengths and shapes of the 9.7 μ m and 18 μ m silicate absorption features make MIR spectral modeling and interpretation challenging, particularly for heavily obscured galaxies. By adopting the basic premise that PAH bands have relatively consistent intrinsic ratios within dusty starbursting galaxies, we can, for the first time, empirically determine the overall shape of the MIR attenuation curve by measuring the differential attenuation at specific PAH wavelengths. Our attenuation model shows PAH emission in most (ultra)luminous infrared galaxies is unambiguously subjected to attenuation, and we find strong evidence that PAH bands undergo differential attenuation as obscuration increases. Compared to preexisting results, the MIR attenuation curve derived from the model favors relatively gray continuum absorption from 3–8 μ m and silicate features with intermediate strength at 9.7 μ m but with stronger than typical 18 μ m opacity.

Published
2024
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4. JWST Observations of Starbursts: Polycyclic Aromatic Hydrocarbon Emission at the Base of the M82 Galactic Wind

Author

Alberto D. Bolatto, Rebecca C. Levy, Elizabeth Tarantino, Martha L. Boyer, Deanne B. Fisher, Serena A. Cronin, Adam K. Leroy, Ralf S. Klessen, J. D. Smith, Danielle A. Berg, Torsten Böker, Leindert A. Boogaard, Eve C. Ostriker, Todd A. Thompson, Juergen Ott, Laura Lenkić, Laura A. Lopez, Daniel A. Dale, Sylvain Veilleux, Paul P. van der Werf, Simon C. O. Glover, Karin M. Sandstrom, Evan D. Skillman, John Chisholm, Vicente Villanueva, Thomas S.-Y. Lai, Sebastian Lopez, Elisabeth A. C. Mills, Kimberly L. Emig, Lee Armus, Divakara Mayya, David S. Meier, Ilse De Looze, Rodrigo Herrera-Camus, Fabian Walter, Mónica Relaño, Hannah B. Koziol, Joshua Marvil, María J. Jiménez-Donaire, and Paul Martini

Subjects
Luminous infrared galaxies, Galaxy winds, Starburst galaxies, Dust physics, Interstellar medium, Astrophysics, QB460-466
Abstract

We present new observations of the central 1 kpc of the M82 starburst obtained with the James Webb Space Telescope near-infrared camera instrument at a resolution θ ∼ 0.″05–0.″1 (∼1–2 pc). The data comprises images in three mostly continuum filters (F140M, F250M, and F360M), and filters that contain [Fe ii ] (F164N), H _2 v = 1 → 0 (F212N), and the 3.3 μ m polycyclic aromatic hydrocarbon (PAH) feature (F335M). We find prominent plumes of PAH emission extending outward from the central starburst region, together with a network of complex filamentary substructures and edge-brightened bubble-like features. The structure of the PAH emission closely resembles that of the ionized gas, as revealed in Paschen α and free–free radio emission. We discuss the origin of the structure, and suggest the PAHs are embedded in a combination of neutral, molecular, and photoionized gas.

Published
2024
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5. GOALS-JWST: Mid-infrared Molecular Gas Excitation Probes the Local Conditions of Nuclear Star Clusters and the Active Galactic Nucleus in the LIRG VV 114

Author

Victorine A. Buiten, Paul P. van der Werf, Serena Viti, Lee Armus, Andrew G. Barr, Loreto Barcos-Muñoz, Aaron S. Evans, Hanae Inami, Sean T. Linden, George C. Privon, Yiqing Song, Jeffrey A. Rich, Susanne Aalto, Philip N. Appleton, Torsten Böker, Vassilis Charmandaris, Tanio Diaz-Santos, Christopher C. Hayward, Thomas S.-Y. Lai, Anne M. Medling, Claudio Ricci, and Vivian U

Subjects
Luminous infrared galaxies, Interstellar medium, Astrophysics, QB460-466
Abstract

The enormous increase in mid-IR sensitivity and spatial and spectral resolution provided by the JWST spectrographs enables, for the first time, detailed extragalactic studies of molecular vibrational bands. This opens an entirely new window for the study of the molecular interstellar medium in luminous infrared galaxies (LIRGs). We present a detailed analysis of rovibrational bands of gas-phase CO, H _2 O, C _2 H _2 , and HCN toward the heavily obscured eastern nucleus of the LIRG VV 114, as observed by NIRSpec and the medium resolution spectrograph on the Mid-InfraRed Instrument (MIRI MRS). Spectra extracted from apertures of 130 pc in radius show a clear dichotomy between the obscured active galactic nucleus (AGN) and two intense starburst regions. We detect the 2.3 μ m CO bandheads, characteristic of cool stellar atmospheres, in the star-forming regions, but not toward the AGN. Surprisingly, at 4.7 μ m, we find highly excited CO ( T _ex ≈ 700–800 K out to at least rotational level J = 27) toward the star-forming regions, but only cooler gas ( T _ex ≈ 200 K) toward the AGN. We conclude that only mid-infrared pumping through the rovibrational lines can account for the equilibrium conditions found for CO and H _2 O in the deeply embedded starbursts. Here, the CO bands probe regions with an intense local radiation field inside dusty young massive star clusters or near the most massive young stars. The lack of high-excitation molecular gas toward the AGN is attributed to geometric dilution of the intense radiation from the bright point source. An overview of the relevant excitation and radiative transfer physics is provided in an appendix.

Published
2024
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6. GOALS-JWST: Gas Dynamics and Excitation in NGC 7469 Revealed by NIRSpec

Author

Marina Bianchin, Vivian U, Yiqing Song, Thomas S.-Y. Lai, Raymond P. Remigio, Loreto Barcos-Muñoz, Tanio Díaz-Santos, Lee Armus, Hanae Inami, Kirsten L. Larson, Aaron S. Evans, Torsten Böker, Justin A. Kader, Sean T. Linden, Vassilis Charmandaris, Matthew A. Malkan, Jeff Rich, Thomas Bohn, Anne M. Medling, Sabrina Stierwalt, Joseph M. Mazzarella, David R. Law, George C. Privon, Susanne Aalto, Philip Appleton, Michael J. I. Brown, Victorine A. Buiten, Luke Finnerty, Christopher C. Hayward, Justin Howell, Kazushi Iwasawa, Francisca Kemper, Jason Marshall, Jed McKinney, Francisco Müller-Sánchez, Eric J. Murphy, Paul P. van der Werf, David B. Sanders, and Jason Surace

Subjects
Luminous infrared galaxies, Galaxy nuclei, Active galactic nuclei, Seyfert galaxies, Galaxy winds, Galaxy kinematics, Astrophysics, QB460-466
Abstract

We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe ii ], H _2 , and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H _2 /Br γ and [Fe ii ]/Pa β emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Pa α velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding–feedback process, with a contribution from the radio jet helping to drive the outflow.

Published
2024
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7. GOALS-JWST: Small Neutral Grains and Enhanced 3.3 μm PAH Emission in the Seyfert Galaxy NGC 7469

Author

Thomas S.-Y. Lai, Lee Armus, Marina Bianchin, Tanio Díaz-Santos, Sean T. Linden, George C. Privon, Hanae Inami, Vivian U, Thomas Bohn, Aaron S. Evans, Kirsten L. Larson, Brandon S. Hensley, J.-D. T. Smith, Matthew A. Malkan, Yiqing Song, Sabrina Stierwalt, Paul P. van der Werf, Jed McKinney, Susanne Aalto, Victorine A. Buiten, Jeff Rich, Vassilis Charmandaris, Philip Appleton, Loreto Barcos-Muñoz, Torsten Böker, Luke Finnerty, Justin A. Kader, David R. Law, Anne M. Medling, Michael J. I. Brown, Christopher C. Hayward, Justin Howell, Kazushi Iwasawa, Francisca Kemper, Jason Marshall, Joseph M. Mazzarella, Francisco Müller-Sánchez, Eric J. Murphy, David Sanders, and Jason Surace

Subjects
Seyfert galaxies, Active galactic nuclei, Polycyclic aromatic hydrocarbons, Starburst galaxies, Luminous infrared galaxies, Astrophysics, QB460-466
Abstract

We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) integral field spectroscopy of the nearby luminous infrared galaxy NGC 7469. We take advantage of the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec to study the 3.3 μ m neutral polycyclic aromatic hydrocarbon (PAH) grain emission on ∼200 pc scales. A clear change in the average grain properties between the star-forming ring and the central AGN is found. Regions in the vicinity of the AGN, with [Ne iii ]/[Ne ii ] > 0.25, tend to have larger grain sizes and lower aliphatic-to-aromatic (3.4/3.3) ratios, indicating that smaller grains are preferentially removed by photodestruction in the vicinity of the AGN. PAH emission at the nucleus is weak and shows a low 11.3/3.3 PAH ratio. We find an overall suppression of the total PAH emission relative to the ionized gas in the central 1 kpc region of the AGN in NGC 7469 compared to what has been observed with Spitzer on 3 kpc scales. However, the fractional 3.3 μ m–to–total PAH power is enhanced in the starburst ring, possibly due to a variety of physical effects on subkiloparsec scales, including recurrent fluorescence of small grains or multiple photon absorption by large grains. Finally, the IFU data show that while the 3.3 μ m PAH-derived star formation rate (SFR) in the ring is 27% higher than that inferred from the [Ne ii ] and [Ne iii ] emission lines, the integrated SFR derived from the 3.3 μ m feature would be underestimated by a factor of 2 due to the deficit of PAHs around the AGN, as might occur if a composite system like NGC 7469 were to be observed at high redshift.

Published
2023
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8. GOALS-JWST: Tracing AGN Feedback on the Star-forming Interstellar Medium in NGC 7469

Author

Thomas S.-Y. Lai, Lee Armus, Vivian U, Tanio Díaz-Santos, Kirsten L. Larson, Aaron Evans, Matthew A. Malkan, Philip Appleton, Jeff Rich, Francisco Müller-Sánchez, Hanae Inami, Thomas Bohn, Jed McKinney, Luke Finnerty, David R. Law, Sean T. Linden, Anne M. Medling, George C. Privon, Yiqing Song, Sabrina Stierwalt, Paul P. van der Werf, Loreto Barcos-Muñoz, J. D. T. Smith, Aditya Togi, Susanne Aalto, Torsten Böker, Vassilis Charmandaris, Justin Howell, Kazushi Iwasawa, Francisca Kemper, Joseph M. Mazzarella, Eric J. Murphy, Michael J. I. Brown, Christopher C. Hayward, Jason Marshall, David Sanders, and Jason Surace

Subjects
Seyfert galaxies, Active galactic nuclei, Polycyclic aromatic hydrocarbons, Starburst galaxies, Luminous infrared galaxies, Astrophysics, QB460-466
Abstract

We present James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) integral-field spectroscopy of the nearby merging, luminous infrared galaxy, NGC 7469. This galaxy hosts a Seyfert type-1.5 nucleus, a highly ionized outflow, and a bright, circumnuclear star-forming ring, making it an ideal target to study active galactic nucleus (AGN) feedback in the local universe. We take advantage of the high spatial/spectral resolution of JWST/MIRI to isolate the star-forming regions surrounding the central active nucleus and study the properties of the dust and warm molecular gas on ∼100 pc scales. The starburst ring exhibits prominent polycyclic aromatic hydrocarbon (PAH) emission, with grain sizes and ionization states varying by only ∼30%, and a total star formation rate of 10–30 M _⊙ yr ^−1 derived from fine structure and recombination emission lines. Using pure rotational lines of H _2 we detect 1.2 × 10 ^7 M _⊙ of warm molecular gas at a temperature higher than 200 K in the ring. All PAH bands get significantly weaker toward the central source, where larger and possibly more ionized grains dominate the emission, likely the result of the ionizing radiation and/or the fast wind emerging from the AGN. The small grains and warm molecular gas in the bright regions of the ring however display properties consistent with normal star-forming regions. These observations highlight the power of JWST to probe the inner regions of dusty, rapidly evolving galaxies for signatures of feedback and inform models that seek to explain the coevolution of supermassive black holes and their hosts.

Published
2022
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9. PDRs4All: A JWST Early Release Science Program on Radiative Feedback from Massive Stars

Author

Olivier Berné, Émilie Habart, Els Peeters, Alain Abergel, Edwin A. Bergin, Jeronimo Bernard-Salas, Emeric Bron, Jan Cami, Emmanuel Dartois, Asunción Fuente, Javier R. Goicoechea, Karl D. Gordon, Yoko Okada, Takashi Onaka, Massimo Robberto, Markus Röllig, Alexander G. G. M. Tielens, Sílvia Vicente, Mark G. Wolfire, Felipe Alarcón, C. Boersma, Amélie Canin, Ryan Chown, Daniel Dicken, David Languignon, Romane Le Gal, Marc W. Pound, Boris Trahin, Thomas Simmer, Ameek Sidhu, Dries Van De Putte, Sara Cuadrado, Claire Guilloteau, Alexandros Maragkoudakis, Bethany R. Schefter, Thiébaut Schirmer, Stéphanie Cazaux, Isabel Aleman, Louis Allamandola, Rebecca Auchettl, Giuseppe Antonio Baratta, Salma Bejaoui, Partha P. Bera, Goranka Bilalbegović, John H. Black, Francois Boulanger, Jordy Bouwman, Bernhard Brandl, Philippe Brechignac, Sandra Brünken, Andrew Burkhardt, Alessandra Candian, Jose Cernicharo, Marin Chabot, Shubhadip Chakraborty, Jason Champion, Sean W. J. Colgan, Ilsa R. Cooke, Audrey Coutens, Nick L. J. Cox, Karine Demyk, Jennifer Donovan Meyer, Cécile Engrand, Sacha Foschino, Pedro García-Lario, Lisseth Gavilan, Maryvonne Gerin, Marie Godard, Carl A. Gottlieb, Pierre Guillard, Antoine Gusdorf, Patrick Hartigan, Jinhua He, Eric Herbst, Liv Hornekaer, Cornelia Jäger, Eduardo Janot-Pacheco, Christine Joblin, Michael Kaufman, Francisca Kemper, Sarah Kendrew, Maria S. Kirsanova, Pamela Klaassen, Collin Knight, Sun Kwok, Álvaro Labiano, Thomas S.-Y. Lai, Timothy J. Lee, Bertrand Lefloch, Franck Le Petit, Aigen Li, Hendrik Linz, Cameron J. Mackie, Suzanne C. Madden, Joëlle Mascetti, Brett A. McGuire, Pablo Merino, Elisabetta R. Micelotta, Karl Misselt, Jon A. Morse, Giacomo Mulas, Naslim Neelamkodan, Ryou Ohsawa, Alain Omont, Roberta Paladini, Maria Elisabetta Palumbo, Amit Pathak, Yvonne J. Pendleton, Annemieke Petrignani, Thomas Pino, Elena Puga, Naseem Rangwala, Mathias Rapacioli, Alessandra Ricca, Julia Roman-Duval, Joseph Roser, Evelyne Roueff, Gaël Rouillé, Farid Salama, Dinalva A. Sales, Karin Sandstrom, Peter Sarre, Ella Sciamma-O’Brien, Kris Sellgren, Matthew J. Shannon, Sachindev S. Shenoy, David Teyssier, Richard D. Thomas, Aditya Togi, Laurent Verstraete, Adolf N. Witt, Alwyn Wootten, Nathalie Ysard, Henning Zettergren, Yong Zhang, Ziwei E. Zhang, Junfeng Zhen, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Western Ontario (UWO), Carl Sagan Center, SETI Institute, University of Michigan [Ann Arbor], University of Michigan System, Analytic and Computational Research, Inc. - Earth Sciences (ACRI-ST), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Observatorio Astronomico Nacional, Madrid, Instituto de Física Fundamental [Madrid] (IFF), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Universiteit Gent = Ghent University (UGENT), Space Telescope Science Institute (STSci), Physikalisches Institut [Köln], Universität zu Köln = University of Cologne, Meisei University, The University of Tokyo (UTokyo), Leiden Observatory [Leiden], Universiteit Leiden, Johns Hopkins University (JHU), Instituto de Astrofísica e Ciências do Espaço (IASTRO), University of Maryland [College Park], University of Maryland System, NASA Ames Research Center (ARC), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Signal et Communications (IRIT-SC), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), Institut National Polytechnique (Toulouse) (Toulouse INP), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Delft University of Technology (TU Delft), Universidade Federal de Itajubá, Bay Area Environmental Research Institute (BAER), Australian Synchrotron [Clayton], INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), University of Zagreb, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), University of Colorado [Boulder], Institute for Molecules and Materials [Nijmegen], Radboud University [Nijmegen], Wellesley College, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), University of British Columbia (UBC), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), European Space Astronomy Centre (ESAC), Agence Spatiale Européenne = European Space Agency (ESA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Rice University [Houston], Yunnan Observatories, Chinese Academy of Sciences [Changchun Branch] (CAS), Universidad de Chile = University of Chile [Santiago] (UCHILE), University of Virginia, Aarhus University [Aarhus], Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Instituto de Astronomia, Geofísica e Ciências Atmosféricas [São Paulo] (IAG), Universidade de São Paulo = University of São Paulo (USP), San Jose State University [San Jose] (SJSU), European Southern Observatory (ESO), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Academia Sinica, Institute of Astronomy of the Russian Academy of Sciences (INASAN), Russian Academy of Sciences [Moscow] (RAS), UK Astronomy Technology Centre (UK ATC), Science and Technology Facilities Council (STFC), Telespazio, Services par satellites, Infrared Processing and Analysis Center (IPAC), California Institute of Technology (CALTECH), University of Missouri [Columbia] (Mizzou), University of Missouri System, Max Planck Institute for Astronomy (MPIA), CAS Key Laboratory of Crust–Mantle Materials and Environments [Hefei], School of Earth and Space Sciences [Hefei], University of Science and Technology of China [Hefei] (USTC)-University of Science and Technology of China [Hefei] (USTC)-Chinese Academy of Sciences [Beijing] (CAS), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), University of California [Berkeley] (UC Berkeley), University of California (UC), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut des Sciences Moléculaires (ISM), Université Montesquieu - Bordeaux 4-Université Sciences et Technologies - Bordeaux 1 (UB)-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Massachusetts Institute of Technology (MIT), Instituto de Ciencia de Materiales de Madrid (ICMM), Helsingin yliopisto = Helsingfors universitet = University of Helsinki, Steward Observatory, University of Arizona, INAF - Osservatorio Astronomico di Cagliari (OAC), United Arab Emirates University (UAEU), National Astronomical Observatory of Japan (NAOJ), Banaras Hindu University [Varanasi] (BHU), University of Amsterdam [Amsterdam] (UvA), Laboratoire de Chimie et Physique Quantiques Laboratoire (LCPQ), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Universidade Federal do Rio Grande do Sul [Porto Alegre] (UFRGS), University of California [San Diego] (UC San Diego), University of Nottingham, UK (UON), Ohio State University [Columbus] (OSU), Space Science Institute [Boulder] (SSI), Stockholm University, Texas State University, Ritter Astrophysical Research Center, University of Toledo, National Sun Yat-Sen University (NSYSU), Star and Planet Formation Laboratory, ITA, USA, GBR, FRA, DEU, ESP, AUS, BEL, BRA, CHL, TWN, HRV, DNK, JPN, IND, NLD, PRT, CHN, RUS, SWE, National Aeronautics and Space Administration (US), University of Maryland, University of Michigan, Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Natural Sciences and Engineering Research Council of Canada, Ministerio de Ciencia e Innovación (España), German Research Foundation, Japan Society for the Promotion of Science, San José State University Research Foundation, Berné, Olivier, Habart, Émilie, Peeters, Els, Abergel, Alain, Bergin, Edwin A., Bernard-Salas, Jeronimo, Bron, Emeric, Cami, Jan, Dartois, Emmanuel, Fuente, Asunción, Goicoechea, Javier R., Gordon, Karl D., Okada, Yoko, Onaka, Takashi, Robberto, Massimo, Röllig, Markus, Tielens, Alexander G.G.M., Vicente, Sílvia, Wolfire, Mark G., Alarcón, Felipe, Boersma, C., Canin, Amélie, Chown, Ryan, Dicken, Daniel, Le Gal, Romane, Pound, Marc W., Trahin, Boris, Sidhu, Ameek, Van De Putte, Dries, Cuadrado, Sara, Guilloteau, Claire, Maragkoudakis, Alexandros, Schefter, Bethany R., Schirmer, Thiébaut, Aleman, Isabel, Allamandola, Louis, Auchettl, Rebecca, Antonio Baratta, Giuseppe, Bejaoui, Salma, Bera, Partha P., Bilalbegović, Goranka, Black, John H., Boulanger, Francois, Bouwman, Jordy, Brandl, Bernhard, Brünken, Sandra, Burkhardt, Andrew, Candian, Alessandra, Cernicharo, José, Chakraborty, Shubhadip, Champion, Jason, Colgan, Sean W.J., Cooke, Ilsa R., Coutens, Audrey, Cox, Nick L.J., Demyk, Karine, Donovan Meyer, Jennifer, Engrand, Cécile, Foschino, Sacha, Gavilan, Lisseth, Gerin, Maryvonne, Godard, Marie, Gottlieb, Carl A., Guillard, Pierre, Gusdorf, Antoine, Hartigan, Patrick, He, Jinhua, Herbst, Eric, Hornekaer, Liv, Janot-Pacheco, Eduardo, Joblin, Christine, Kaufman, Michael, Kemper, Francisca, Kendrew, Sarah, Kirsanova, Maria S., Klaassen, Pamela, Knight, Collin, Kwok, Sun, Labiano, Álvaro, Lai, Thomas S.Y., Lee, Timothy J., Lefloch, Bertrand, Le Petit, Franck, Li, Aigen, Linz, Hendrik, MacKie, Cameron J., Madden, Suzanne C., Mascetti, Joëlle, McGuire, Brett A., Merino, Pablo, Micelotta, Elisabetta R., Morse, Jon A., Molecular Spectroscopy (HIMS, FNWI), and HIMS (FNWI)

Subjects
Gaseous Nebulae, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, FELIX Infrared and Terahertz Spectroscopy, Star Forming Regions, Astrophysics - Astrophysics of Galaxies, Infrared Telescopes, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, [INFO]Computer Science [cs], Photodissociation Regions, Astrophysics::Earth and Planetary Astrophysics, Polycyclic Aromatic Hydrocarbons, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], James Webb Space Telescope (JWST), Photo-Dissociation Regions (PDRs), Massive stars, Orion Bar, MIRI, NIRSpec, NIRCam, Astrophysics::Galaxy Astrophysics
Abstract

22 pags., 8 figs., 1 tab., Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter-and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template data sets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template data sets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations., Support for JWST-ERS program ID 1288 was provided through grants from the STScI under NASA contract NAS5-03127 to STScI (K.G., D.V.D.P., M.R.), Univ. of Maryland (M.W., M.P.), Univ. of Michigan (E.B., F.A.), and Univ. of Toledo (T.S.-Y.L.). O.B. and E.H. are supported by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES, and through APR grants 6315 and 6410 provided by CNES. E. P. and J.C. acknowledge support from the National Science and Engineering Council of Canada (NSERC) Discovery Grant program (RGPIN-2020-06434 and RGPIN-2021-04197 respectively). E.P. acknowledges support from a Western Strategic Support Accelerator Grant (ROLA ID 0000050636). J.R.G. and S.C. thank the Spanish MCINN for funding support under grant PID2019-106110GB-I00. Work by M.R. and Y.O. is carried out within the Collaborative Research Centre 956, subproject C1, funded by the Deutsche Forschungsgemeinschaft (DFG)—project ID 184018867. T.O. acknowledges support from JSPS Bilateral Program, grant No. 120219939. M.P. and M.W. acknowledge support from NASA Astrophysics Data Analysis Program award #80NSSC19K0573. C.B. is grateful for an appointment at NASA Ames Research Center through the San José State University Research Foundation (NNX17AJ88A) and acknowledges support from the Internal Scientist Funding Model (ISFM) Directed Work Package at NASA Ames titled: “Laboratory Astrophysics—The NASA Ames PAH IR Spectroscopic Database.”

Published
2022
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10. Are the carriers of diffuse interstellar bands and extended red emission the same?

Author

Jan Cami, Adolf N. Witt, Thomas S. Y. Lai, and Carlos Alvarez

Subjects
Physics, Nebula, fungi, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Photodissociation region, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Fluorescence, Ion, Interstellar medium, Wavelength, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Excited state, 0103 physical sciences, 010306 general physics, Ground state, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We report the first spectroscopic observations of a background star seen through the region between the ionization front and the dissociation front of the nebula IC 63. This photodissociation region (PDR) exhibits intense extended red emission (ERE) attributed to fluorescence by large molecules/ions. We detected strong diffuse interstellar bands (DIB) in the stellar spectrum, including an exceptionally strong and broad DIB at $\lambda$4428. The detection of strong DIBs in association with ERE could be consistent with the suggestion that the carriers of DIBs and ERE are identical. The likely ERE process is recurrent fluorescence, enabled by inverse internal conversions from highly excited vibrational levels of the ground state to low-lying electronic states with subsequent transitions to ground. This provides a path to rapid radiative cooling for molecules/molecular ions, greatly enhancing their ability to survive in a strongly irradiated environment. The ratio of the equivalent widths (EW) of DIBs $\lambda$5797 and $\lambda$5780 in IC 63 is the same as that observed in the low-density interstellar medium with UV interstellar radiation fields (ISRF) weaker by at least two orders of magnitude. This falsifies suggestions that the ratio of these two DIBs can serve as a measure of the UV strength of the ISRF. Observations of the nebular spectrum of the PDR of IC 63 at locations immediately adjacent to where DIBs were detected failed to reveal any presence of sharp emission features seen in the spectrum of the Red Rectangle nebula. This casts doubts upon proposals that the carriers of these features are the same as those of DIBs seen at slightly shorter wavelengths., Comment: 13 pages, 9 figures

Published
2020
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11. GOALS-JWST

Author

Thomas S.-Y. Lai, Lee Armus, Vivian U, Tanio Díaz-Santos, Kirsten L. Larson, Aaron Evans, Matthew A. Malkan, Philip Appleton, Jeff Rich, Francisco Müller-Sánchez, Hanae Inami, Thomas Bohn, Jed McKinney, Luke Finnerty, David R. Law, Sean T. Linden, Anne M. Medling, George C. Privon, Yiqing Song, Sabrina Stierwalt, Paul P. van der Werf, Loreto Barcos-Muñoz, J. D. T. Smith, Aditya Togi, Susanne Aalto, Torsten Böker, Vassilis Charmandaris, Justin Howell, Kazushi Iwasawa, Francisca Kemper, Joseph M. Mazzarella, Eric J. Murphy, Michael J. I. Brown, Christopher C. Hayward, Jason Marshall, David Sanders, Jason Surace, National Science Foundation (US), National Aeronautics and Space Administration (US), Japan Society for the Promotion of Science, Simons Foundation, Ministerio de Ciencia, Innovación y Universidades (España), and Agencia Estatal de Investigación (España)

Subjects
Active galactic nuclei, Seyfert galaxies, Space and Planetary Science, Astronomy and Astrophysics, Starburst galaxies, Astrophysics - Astrophysics of Galaxies, Polycyclic aromatic hydrocarbons, Luminous infrared galaxies
Abstract

We present James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) integral-field spectroscopy of the nearby merging, luminous infrared galaxy, NGC 7469. This galaxy hosts a Seyfert type-1.5 nucleus, a highly ionized outflow, and a bright, circumnuclear star-forming ring, making it an ideal target to study active galactic nucleus (AGN) feedback in the local universe. We take advantage of the high spatial/spectral resolution of JWST/MIRI to isolate the star-forming regions surrounding the central active nucleus and study the properties of the dust and warm molecular gas on ∼100 pc scales. The starburst ring exhibits prominent polycyclic aromatic hydrocarbon (PAH) emission, with grain sizes and ionization states varying by only ∼30%, and a total star formation rate of 10–30 M⊙ yr−1 derived from fine structure and recombination emission lines. Using pure rotational lines of H2 we detect 1.2 × 107 M⊙ of warm molecular gas at a temperature higher than 200 K in the ring. All PAH bands get significantly weaker toward the central source, where larger and possibly more ionized grains dominate the emission, likely the result of the ionizing radiation and/or the fast wind emerging from the AGN. The small grains and warm molecular gas in the bright regions of the ring however display properties consistent with normal star-forming regions. These observations highlight the power of JWST to probe the inner regions of dusty, rapidly evolving galaxies for signatures of feedback and inform models that seek to explain the coevolution of supermassive black holes and their hosts., This work is based on observations made with the NASA/ESA/CSA JWST. T.S.-Y.L. acknowledges funding support from NASA grant JWST-ERS-01328. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program #1328 and can be accessed via doi:10.17909/0fe2-cf33. V.U. acknowledges funding support from NASA Astrophysics Data Analysis Program (ADAP) grant 80NSSC20K0450. The Flatiron Institute is supported by the Simons Foundation. H.I. and T.B. acknowledge support from JSPS KAKENHI grant No. JP21H01129 and the Ito Foundation for Promotion of Science. A.M.M. acknowledges support from the National Science Foundation under grant No. 2009416. A.S.E. and S.L. acknowledge support from NASA grant HST-GO15472 and HST-GO16914. Y.S. was funded in part by the NSF through the Grote Reer Fellowship Program administered by Associated Universities, Inc./National Radio Astronomy Observatory. S.A. gratefully acknowledges support from an ERC Advanced grant 789410, from the Swedish Research Council and from the Knut and Alice Wallenberg (KAW) Foundation. F.K. acknowledges support from the Spanish program Unidad de Excelencia María de Maeztu CEX2020-001058-M, financed by MCIN/AEI/10.13039/501100011033. K.I. acknowledges support by the Spanish MCIN under grant PID2019-105510GB-C33/AEI/10.13039/501100011033. F.M-S. acknowledges support from NASA through ADAP award 80NSSC19K1096. Finally, this research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Published
2022

12. Extended Red Emission: Observational constraints for models

Author

Thomas S.-Y. Lai and Adolf N. Witt

Subjects
Physics, Milky Way, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Galaxy, Cosmology, Interstellar medium, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Observational study, Optical emission spectroscopy, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Extended Red Emission (ERE) is a widely observed optical emission process, present in a wide range of circumstellar and interstellar environments in the Milky Way galaxy as well as other galaxies. Definitive identifications of the ERE carriers and the ERE process are still a matter of debate. Numerous models have been proposed in recent decades, often developed without consideration of the growing body of observational constraints, which by now invalidate many of these models. This review focuses on the most well-established observational constraints which should help to delineate the way toward a generally accepted explanation of the ERE and an understanding of its place in the radiation physics of the interstellar medium., Comment: 10 pages, 2 figures, preprint to be published in the Topical Collection on "Unexplained Spectral Phenomena in the Interstellar Medium" of Astrophysics and Space Science

Published
2020
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13. All the PAHs: an AKARI-Spitzer Cross Archival Spectroscopic Survey of Aromatic Emission in Galaxies

Author

J. D. T. Smith, Thomas S.-Y. Lai, Shunsuke Baba, Masatoshi Imanishi, and Henrik Spoon

Subjects
Physics, Luminous infrared galaxy, 010504 meteorology & atmospheric sciences, Star formation, Metallicity, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Redshift, Galaxy, Spectral line, Luminosity, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Dwarf galaxy
Abstract

We present a large sample of 2.5-38 $\mu m$ galaxy spectra drawn from a cross-archival comparison in the AKARI-Spitzer Extragalactic Spectral Survey (ASESS), and investigate a subset of 113 star-forming galaxies with prominent polycyclic aromatic hydrocarbon (PAH) emission spanning a wide range of star formation properties. With AKARI's extended 2.5-5 $\mu m$ wavelength coverage, we self-consistently model for the first time all PAH emission bands using a modified version of PAHFIT. We find $L_\mathrm{PAH\,3.3}/L_\mathrm{IR}$ $\sim$ 0.1% and the 3.3 $\mu m$ PAH feature contributes $\sim$1.5-3% to the total PAH power -- somewhat less than earlier dust models have assumed. We establish a calibration between 3.3 $\mu m$ PAH emission and star formation rate, but also find regimes where it loses reliability, including at high luminosity and low metallicity. The 3.4 $\mu m$ aliphatic emission and a broad plateau feature centered at 3.47 $\mu m$ are also modeled. As the shortest wavelength PAH feature, 3.3 $\mu m$ is susceptible to attenuation, leading to a factor of $\sim$ 3 differences in the inferred star formation rate at high obscuration with different assumed attenuation geometries. Surprisingly, $L_\mathrm{PAH\, 3.3} / L_\mathrm{\Sigma\, PAH}$ shows no sign of decline at high luminosities, and the low metallicity dwarf galaxy II Zw 40 exhibits an unusually strong 3.3 $\mu m$ band; both results suggest either that the smallest PAHs are better able to survive under intense radiation fields than presumed, or that PAH emission is shifted to shorter wavelengths in intense and high energy radiation environments. A photometric surrogate for 3.3 $\mu m$ PAH luminosity using JWST/NIRCam is provided and found to be highly reliable at low redshift., Comment: 29 pages, 18 figures, accepted in ApJ

Published
2020
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14. Extended Red Emission in IC59 and IC63

Author

Ken Crawford, Adolf N. Witt, and Thomas S. Y. Lai

Subjects
Physics, Photoluminescence, Photon, Infrared, Extinction (astronomy), FOS: Physical sciences, Astronomy and Astrophysics, Radiation, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Interstellar medium, Internal conversion, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Atomic physics, 010306 general physics, 010303 astronomy & astrophysics, Excitation, Astrophysics::Galaxy Astrophysics
Abstract

We analysed new wide-field, wide- and narrow-band optical images of IC 59 and IC 63, two nebulae which are externally illuminated by the early B-star {\gamma} Cas, with the objective of mapping the extended red emission (ERE), a dust-related photoluminescence process that is still poorly understood, in these two clouds. The spatial distribution of the ERE relative to the direction of the incident radiation and relative to other emission processes, whose carriers and excitation requirements are known, provides important constraints on the excitation of the ERE. In both nebulae, we find the ERE intensity to peak spatially well before the more extended distribution of mid-infrared emission in the unidentified infrared bands, supporting earlier findings that point toward far-ultraviolet (11 eV < E$_\mathrm{{photon}}$ < 13.6 eV) photons as the source of ERE excitation. The band-integrated absolute intensities of the ERE in IC 59 and IC 63 measured relative to the number density of photons available for ERE excitation are lower by about two orders of magnitude compared to ERE intensities observed in the high-latitude diffuse interstellar medium (ISM). This suggests that the lifetime of the ERE carriers is significantly reduced in the more intense radiation field prevailing in IC 59 and IC 63, pointing toward potential carriers that are only marginally stable against photo-processing under interstellar conditions. A model involving isolated molecules or molecular ions, capable of inverse internal conversion and recurrent fluorescence, appears to provide the most likely explanation for our observational results., Comment: 19 pages, 11 figures, accepted for publication in MNRAS

Published
2017

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