Статті в журналах: "Extended emission-line regions"

1

Stockton, Alan, Hai Fu, and Gabriela Canalizo. "QSO extended emission-line regions." New Astronomy Reviews 50, no. 9-10 (November 2006): 694–700. http://dx.doi.org/10.1016/j.newar.2006.06.024.

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2

Robinson, A. "Extended Emission-Line Regions Around AGN." International Astronomical Union Colloquium 159 (1997): 280–87. http://dx.doi.org/10.1017/s0252921100040288.

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AbstractHigh-excitation extended emission-line nebulae around active galactic nuclei probably result either from photoionization of the interstellar medium by beamed continuum radiation, or dynamical interactions between radio sources and the ambient gas, or both. Here I discuss the models based on these mechanisms, and their relative importance in radio-quiet and radio-loud active galaxies.

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3

Stockton, Alan, and John W. MacKenty. "Extended emission-line regions around QSOs." Astrophysical Journal 316 (May 1987): 584. http://dx.doi.org/10.1086/165227.

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4

Hutchings, J. B., and P. Hickson. "Extended emission-line regions in active galaxies." Astronomical Journal 95 (May 1988): 1363. http://dx.doi.org/10.1086/114733.

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5

Inskip, K. J., M. Villar-Martín, C. Tadhunter, J. Holt, and R. Morganti. "The origin of extended emission line regions." New Astronomy Reviews 51, no. 1-2 (February 2007): 47–51. http://dx.doi.org/10.1016/j.newar.2006.10.004.

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6

Fu, Hai, and Alan Stockton. "EXTENDED EMISSION-LINE REGIONS: REMNANTS OF QUASAR SUPERWINDS?" Astrophysical Journal 690, no. 1 (December 1, 2008): 953–73. http://dx.doi.org/10.1088/0004-637x/690/1/953.

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7

Husemann, B., L. Wisotzki, S. F. Sánchez, and K. Jahnke. "Extended emission-line regions in low-redshift quasars." Astronomy & Astrophysics 488, no. 1 (July 9, 2008): 145–49. http://dx.doi.org/10.1051/0004-6361:200810276.

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8

Fu, Hai, and Alan Stockton. "A Common Origin for Quasar Extended Emission-Line Regions and Their Broad-Line Regions." Astrophysical Journal 664, no. 2 (July 18, 2007): L75—L78. http://dx.doi.org/10.1086/520959.

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9

Evans, Ian, Anuradha Koratkar, Mark Allen, Zlatan Tsvetanov, and Michael Dopita. "Excitation Mechanism of Extended Emission-Line Regions in Active Galaxies." International Astronomical Union Colloquium 159 (1997): 386–89. http://dx.doi.org/10.1017/s0252921100040537.

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AbstractPhotoionization and shock models of the extended emissionline regions (EELRs) in active galaxies demonstrate that the optical emission lines alone are a poor discriminant of the excitation mechanism. Combining optical and UV data provides a discriminant between nuclear photoionization and autoionizing shock models. Hubble Space Telescope UV spectrophotometry of two Seyferts suggests that the EELRs in these objects are probably photoionized by the nucleus.

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10

Breugel, Wil van. "Extended optical line emission associated with radio galaxies." Canadian Journal of Physics 64, no. 4 (April 1, 1986): 392–97. http://dx.doi.org/10.1139/p86-070.

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Observations of radio galaxies that have extended optical emission-line regions provide a new way of studying the interaction of extragalactic jets with their ambient medium. Their general properties are briefly reviewed and are illustrated using recent results on 4C 29.30 and Minkowski's Object.

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11

Bicknell, G. V. "The Emission-line Filaments in Centaurus A." Publications of the Astronomical Society of Australia 9, no. 1 (1991): 93–94. http://dx.doi.org/10.1017/s1323358000025029.

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AbstractThis paper examines recent investigations of emission-line filaments along the edge of the radio source in Centaurus A. It shows how these studies have ramifications for the excitation of the narrow line regions and extended emission-line regions of other active galaxies.

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12

Percival, S. M., and P. A. James. "Diffuse LINER-type emission from extended disc regions of barred galaxies." Monthly Notices of the Royal Astronomical Society 496, no. 1 (May 30, 2020): 36–48. http://dx.doi.org/10.1093/mnras/staa1369.

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ABSTRACT We present a spectroscopic analysis of the central disc regions of barred spiral galaxies, concentrating on the region that is swept by the bar but not including the bar itself (the ‘star formation desert’ or SFD region). New spectroscopy is presented for 34 galaxies, and the full sample analysed comprises 48 SBa–SBcd galaxies. These data confirm the full suppression of SF within the SFD regions of all but the latest type (SBcd) galaxies. However, diffuse [N ii] and H α line emission is detected in all galaxies. The ubiquity and homogeneous properties of this emission from SBa to SBc galaxies favour post-asymptotic giant branch (p-AGB) stars as the source of this line excitation, rather than extreme blue horizontal branch stars. The emission-line ratios strongly exclude any contribution from recent SF, but are fully consistent with recent population synthesis modelling of p-AGB emission by other authors, and favour excitation dominated by ambient gas of approximately solar abundance, rather than ejecta from the AGB stars themselves. The line equivalent widths are also larger than those observed in many fully passive (e.g. elliptical) galaxies, which may also be a consequence of a greater ambient gas density in the SFD regions.

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13

Pécontal, E., P. Ferruit, and A. S. Wilson. "Impact of nuclear activity on extended emission line regions of nearby galaxies." International Astronomical Union Colloquium 149 (1995): 269–73. http://dx.doi.org/10.1017/s0252921100023113.

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AbstractWe used the integral field TIGER to map the intensity ratios of emission lines and the velocity field over the narrow emission line of a few nearby Seyfert galaxies. Our aim is to study the impact of nuclear activity on galaxies, which will hopefully help us to probe the central engine. We present here some results for two objects: M 51 and NGC 5929.

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14

Acosta-Pulido, Jos� A. "Testing the Anisotropy of the central engine from extended emission line regions." Astrophysics and Space Science 205, no. 1 (1993): 195–201. http://dx.doi.org/10.1007/bf00657977.

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15

Shields, Joseph C. "Physical Properties of Extended Emission-Line Regions in Active and Cooling-Flow Galaxies." Publications of the Astronomical Society of the Pacific 104 (May 1992): 384. http://dx.doi.org/10.1086/133008.

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16

Alonso‐Herrero, Almudena, Chris Simpson, Martin J. Ward, and Andrew S. Wilson. "A Near‐Infrared Imaging Study of Seyfert Galaxies with Extended Emission‐Line Regions." Astrophysical Journal 495, no. 1 (March 1998): 196–221. http://dx.doi.org/10.1086/305269.

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17

Wang, QiQi, and Richard G. Kron. "Extended He ii 4686 emission in Markarian 387." Monthly Notices of the Royal Astronomical Society 498, no. 3 (September 14, 2020): 4550–61. http://dx.doi.org/10.1093/mnras/staa2633.

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ABSTRACT In order to explore the effect of an active galactic nucleus (AGN) on the interstellar medium of its host galaxy, we selected a promising case for study, Markarian 387 (Mrk 387), based on the strength of its extended He ii 4686 emission, a high-ionization line that can be excited by a hard source of radiation. We use area-resolved spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey and the availability of additional multiwavelength data. Besides harbouring an obscured AGN and the extended He ii 4686 emission, Mrk 387 has a number of other unusual properties, including a high far-infrared luminosity, a low neutral hydrogen mass compared to the stellar mass, a high Hα luminosity and high Hα equivalent width throughout the disc, and strong He i 5876 in the exterior regions. He ii 4686 and [O iii] 5008 extend with a bilateral morphology beyond 6 kpc from the nucleus. We interpret this emission as due to photoionization from the central source, where the interstellar medium must be sufficiently porous to allow the ionizing flux to reach these relatively distant regions.

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18

Hayashi, T., H. Ohtani, H. Sugai, T. Ishigaki, S. Ozaki, T. Hattori, M. Sasaki, K. Aoki, and M. Yoshida. "3.30. Tridimensional spectroscopy of ionized gases surrounding the low luminosity Seyfert 2 nucleus of NGC2273." Symposium - International Astronomical Union 184 (1998): 149–50. http://dx.doi.org/10.1017/s0074180900084436.

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Seyfert galaxies often have extended emission line regions around their nucleus. We started an observation program of optical tridimensional spectroscopy for circumnuclear regions of nearby Seyfert galaxies to investigate the ionization source of the gas of just vicinity(typically several hundred pc) of nucleus.

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19

Cohen, M. H., H. D. Tran, P. M. Ogle, and R. W. Goodrich. "Optical Polarization of 3C 265." Symposium - International Astronomical Union 175 (1996): 223–26. http://dx.doi.org/10.1017/s0074180900080578.

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3C 265 is a high-redshift (z=0.811) radio galaxy showing extended emission line regions (EELR) to 50 kpc from the nucleus (McCarthy et al 1995). However, it does not show the alignment effect (McCarthy 1993) that is common in distant galaxies: the EELR is not extended along the radio axis.

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20

Koekemoer, A. M., and G. V. Bicknell. "Dynamical Models of Emission-Line Gas in Radio Galaxies." Symposium - International Astronomical Union 175 (1996): 471–72. http://dx.doi.org/10.1017/s0074180900081523.

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Extended emission-line regions (EELRs) in radio ellipticals are generally thought to trace gas acquired externally, eg. through interaction with a gas-rich disk galaxy (Athanassoula and Bosma 1985, Barnes and Hernquist 1992, Hernquist and Mihos 1995). We examine here the dynamical evolution of gas in mergers, focussing on the conditions required for collisions between streams of gas. We find that such collisions can occur over a relatively wide range of encounter geometries, producing large-velocity-amplitude kinematic signatures characteristic of those observed in EELRs. This is relevant to the formation of shocks, which can account for the ionization properties of EELRs (Koekemoer and Bicknell, this conference).

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21

Sun, Ai-Lei, Jenny E. Greene, Nadia L. Zakamska, Andy D. Goulding, Michael A. Strauss, Song Huang, Sean D. Johnson, et al. "Imaging extended emission-line regions of obscured AGN with the Subaru Hyper Suprime-Cam Survey." Monthly Notices of the Royal Astronomical Society 480, no. 2 (May 28, 2018): 2302–23. http://dx.doi.org/10.1093/mnras/sty1394.

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22

Klöckner, Hans-Rainer, and Willem A. Baan. "EVN Observations of the OH megamaser galaxies Mrk 231 and IC 694." Symposium - International Astronomical Union 206 (2002): 430–33. http://dx.doi.org/10.1017/s0074180900222833.

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We present EVN observations of hydroxyl (OH) main-line emission in two megamaser sources Mrk 231 and IC 694. The observations indicate that the broad maser emission lines originate within the nuclear regions. A single 1667 MHz main-line feature is seen at the nucleus of IC 694. In Mrk 231 both main-lines were observed in an extended “half-circular” region of 150 pc by 50 pc surrounding the radio nucleus.

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23

Yamauchi, S. "Hot Plasma in the Galaxy." Symposium - International Astronomical Union 188 (1998): 47–50. http://dx.doi.org/10.1017/s0074180900114408.

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In the X-ray band, we can see weak and extended X-rays along the Galactic plane and near the Galactic Bulge region, although these regions are dominated by many point sources (e.g., Warwick et al. 1985). The Tenma satellite discovered conspicuous emission lines from selected regions near the Galactic plane (Koyama et al. 1986). These lines are identified with K-shell line from He-like Fe, hence the extended emission is attributable to optically thin hot plasmas with temperatures of several keV. The origin of the thin hot plasmas, however, have been debatable, because no class of X-ray objects shows such high temperature plasma emissions. To investigate the origin of the extended X-rays, we are currently observing the Galactic plane regions with the ASCA satellite. In this paper, we report on the ASCA results: the hard X-ray imaging and spectroscopy of the hot plasma in the Galaxy.

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24

Viegas, S. M., and M. A. Prieto. "Probing photoionization models in two well-studied extended emission-line regions: Centaurus A and 3C 227." Monthly Notices of the Royal Astronomical Society 258, no. 3 (October 1, 1992): 483–90. http://dx.doi.org/10.1093/mnras/258.3.483.

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25

Ishigaki, Tsuyoshi, Michitoshi Yoshida, Kentaro Aoki, Hiroshi Ohtani, Hajime Sugai, Tadashi Hayashi, Shinobu Ozaki, Takashi Hattori, and Motomi Ishii. "Tridimensional Spectrophotometric Study of the Extended Emission-Line Regions of the Infrared-Luminous Merger Markarian 266." Publications of the Astronomical Society of Japan 52, no. 1 (February 1, 2000): 185–207. http://dx.doi.org/10.1093/pasj/52.1.185.

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26

Yan, Renbin, and Michael R. Blanton. "The Ionization of the Warm Gas in Early-type Galaxies and Its UV Upturn." Proceedings of the International Astronomical Union 10, H16 (August 2012): 135. http://dx.doi.org/10.1017/s1743921314004967.

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It has long been known that the majority of early-type galaxies contain warm ionized gas producing optical emission lines. These warm ionized gas are spatially extended to kpc scales. Their line ratios satisify the criteria of Low-ionization Nuclear Emission-line Regions (LINERs) on all major line-ratio diagnostic diagrams. However, their ionization mechanism has been hotly debated. Multiple ionization mechanisms can produce the same kind of line ratios, including photoionization by a central AGN, photoionization by hot evolved stars (e.g. post-AGB stars), collisional ionization by fast shocks, photoionization by hot X-ray emitting gas, and conductive heating or turbulent mixing. Therefore, determining the ionization mechanism requires other information.

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27

Shaban, Ahmed, Rongmon Bordoloi, John Chisholm, Soniya Sharma, Keren Sharon, Jane R. Rigby, Michael G. Gladders, et al. "A 30 kpc Spatially Extended Clumpy and Asymmetric Galactic Outflow at z ∼ 1.7." Astrophysical Journal 936, no. 1 (September 1, 2022): 77. http://dx.doi.org/10.3847/1538-4357/ac7c65.

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Abstract We image the spatial extent of a cool galactic outflow with fine-structure Fe ii* emission and resonant Mg ii emission in a gravitationally lensed star-forming galaxy at z = 1.70347. The Fe ii* and Mg ii (continuum-subtracted) emissions span out to radial distances of ∼14.33 and 26.5 kpc, respectively, with maximum spatial extents of ∼21 kpc for Fe ii* emission and ∼30 kpc for Mg ii emission. Mg ii emission is patchy and covers a total area of ∼184 kpc2, constraining the minimum area covered by the outflowing gas to be ∼13% of the total area. Mg ii emission is asymmetric and shows ∼21% more extended emission along the decl. direction. We constrain the covering fractions of the Fe ii* and Mg ii emission as a function of radial distance and characterize them with a power-law model. The Mg ii 2803 emission line shows two kinematically distinct emission components and may correspond to two distinct shells of outflowing gas with a velocity separation of Δv ∼ 400 km s−1. By using multiple images with different magnifications of the galaxy in the image plane, we trace the Fe ii* and Mg ii emissions around three individual star-forming regions. In all cases, both the Fe ii* and Mg ii emissions are more spatially extended compared to the star-forming regions traced by the [O ii] emission. These findings provide robust constraints on the spatial extent of the outflowing gas and, combined with outflow velocity and column density measurements, will give stringent constraints on mass-outflow rates of the galaxy.

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28

Morais, S. G., A. Humphrey, M. Villar Martín, L. Binette та M. Silva. "Electron energy distributions in the extended gas nebulae associated with high-z AGN: Maxwell–Boltzmann versus κ distributions". Monthly Notices of the Royal Astronomical Society 506, № 1 (5 червня 2021): 1389–405. http://dx.doi.org/10.1093/mnras/stab1599.

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ABSTRACT Emission line observations together with photoionization models provide important information about the ionization mechanisms, densities, temperatures, and metallicities in active galactic nuclei (AGN)-ionized gas. Photoionization models usually assume Maxwell–Boltzmann (M–B) electron energy distributions (EED), but it has been suggested that using κ distributions may be more appropriate and could potentially solve the discrepancies in temperatures and abundances found in HII regions and planetary nebulae. We consider the impact of the presence of κ distributions in photoionized nebulae associated with AGN and study how this might affect spectral modelling and abundance analyses for such regions. Using the photoionization code MAPPINGS 1e, we compute models adopting M–B and κ distributions of electron energies and compare the behaviour of emission line ratios for different values of κ, gas metallicity, density, ionization parameter, and SED slope. We find that the choice of EED can have a large impact on some UV and optical emission lines emitted by photoionized nebulae associated with AGN, and that the impact of adopting a κ distribution is strongly dependent on gas metallicity and ionization parameter. We compile a sample of line ratios for 143 type 2 AGN and compare our models against the observed line ratios. We find that for 98 objects, κ distributions provide a better fit to the observed line ratios than M–B distributions. In addition, we find that adopting κ-distributed electron energies results in significant changes in the inferred gas metallicity and ionization parameter in a significant fraction of objects.

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29

Garden, Rognvald P. "An extremely Luminous H2 Flow in the Dr21 Star Forming Region." Symposium - International Astronomical Union 115 (1987): 325–28. http://dx.doi.org/10.1017/s007418090009567x.

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Previously, mapping of the spatial distribution and velocity structure of vibrational molecular hydrogen (H2) line emission has necessarily been restricted to the central outflow region of the Orion Molecular Cloud (e.g. Beckwidth et al. 1983) where the line intensities are an order of magnitude larger than any other presently known H2 emission source. However, an improved understanding of the role played by highly energetic gas flows in sustaining the observed H2 line emission relies heavily on the collection of comparable data on other active star-forming regions. With this view in mind, we have undertaken a detailed H2 line emission survey of the DR21/W75S molecular cloud complex. We considered this region to be one of the best candidates because it was already known to possess a luminosity (Harvey et al. 1977), CO wind velocities (Dickel et al. 1978, Fischer et al. 1985) and extended H2 emission (Fischer et al. 1981) similar to those seen in Orion.

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30

Aoki, K., H. Ohtani, G. Kosugi, and M. Yoshida. "Area Spectroscopy of the Extended Emission Line Region in the Seyfert Galaxy NGC 3516." International Astronomical Union Colloquium 149 (1995): 203–4. http://dx.doi.org/10.1017/s0252921100022958.

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The researches into extended emission line region (EELR) give us the valuable informations about the nucleus. A recent study of the EELR in the Seyfert 1 galaxy NGC 4151 by Yoshida and Ohtani (1993) have revealed that a strongly asymmetric radiation field in this typical Seyfert 1. They have suggested the anisotropy may be caused inside the BLR. It is important to examine if any other Seyfert 1 galaxy has an anisotropic nuclear radiation.The famous Seyfert 1 galaxy NGC 3516 has EELR which extends ∼ 10” on either side of the nucleus. The morphology of the EELR is Z-shape. This nearby (D=38.9Mpc) galaxy is of type SBO for which the object is expected to be free from contamination by HII regions and dust clouds.

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31

Michalitsianos, A. G., and M. Kafatos. "A Review of the R Aquarii System." International Astronomical Union Colloquium 103 (1988): 235–43. http://dx.doi.org/10.1017/s0252921100103525.

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AbstractThe spatially resolved nebula that characterizes the D–type symbiotic R Aquarii has afforded investigators a unique opportunity to probe the extended emission line regions. Its extensive and complex radio morphology, that includes SiO emission from the only symbiotic associated with maser emission, has provided important clues concerning the mass expulsion process in interacting binary radio stars. Infrared, radio, optical, UV and X-ray observations of the system are discussed in context with models which have been proposed to explain the appearance of the brilliant jet.

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32

Bianchi, L., and M. Grewing. "Evidence for extended chromospheres and transition zones in the uv spectra of FK comae stars." Symposium - International Astronomical Union 122 (1987): 363–66. http://dx.doi.org/10.1017/s0074180900156724.

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The chromospheres and transition zones of the fast rotating giants of the FK Comae type can be studied by analysing their ultraviolet emission line spectra. From relative line intensities, electron densities of the order of 1010to 1011cm−1 are found for the region where the Si IV emission arises. The sizes of the chromospheres and transition regions can be inferred from the emission measure distribution, and a temperature-height relation can be found on the assumption that hydrostatic equilibrium holds. We find the atmospheres of these stars to be clearly more extended than those of normal giant stars, and the flux in the higher excitation chromospheric and transition zone lines (e.g. C II, C IV, Si IV) is significantly stronger than in other stars of similar spectral type. Indeed, the location of these stars in the standard rotation-activity-correlation diagrams places them close to or even above the saturation limit for main sequence stars.

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33

Espinosa-Ponce, C., S. F. Sánchez, C. Morisset, J. K. Barrera-Ballesteros, L. Galbany, R. García-Benito, E. A. D. Lacerda, and D. Mast. "H ii regions in the CALIFA survey: I. catalogue presentation." Monthly Notices of the Royal Astronomical Society 494, no. 2 (March 20, 2020): 1622–46. http://dx.doi.org/10.1093/mnras/staa782.

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ABSTRACT We present a new catalogue of H ii regions based on the integral field spectroscopy (IFS) data of the extended CALIFA and PISCO samples. The selection of H ii regions was based on two assumptions: a clumpy structure with high contrast of H α emission and an underlying stellar population comprising young stars. The catalogue provides the spectroscopic information of 26 408 individual regions corresponding to 924 galaxies, including the flux intensities and equivalent widths of 51 emission lines covering the wavelength range between 3745 and 7200 Å. To our knowledge, this is the largest catalogue of spectroscopic properties of H ii regions. We explore a new approach to decontaminate the emission lines from diffuse ionized gas contribution. This diffuse gas correction was estimated to correct every emission line within the considered spectral range. With the catalogue of H ii regions corrected, new demarcation lines are proposed for the classical diagnostic diagrams. Finally, we study the properties of the underlying stellar populations of the H ii regions. It was found that there is a direct relationship between the ionization conditions on the nebulae and the properties of stellar populations besides the physicals condition on the ionized regions.

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34

Brinkmann, N., F. Wyrowski, J. Kauffmann, D. Colombo, K. M. Menten, X. D. Tang, and R. Güsten. "An imaging line survey of OMC-1 to OMC-3." Astronomy & Astrophysics 636 (April 2020): A39. http://dx.doi.org/10.1051/0004-6361/201936885.

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Context. Recently, sensitive wide-bandwidth receivers in the millimetre regime have enabled us to combine large spatial and spectral coverage for observations of molecular clouds. The resulting capability to map the distributions of lines from many molecules simultaneously yields unbiased coverage of the various environments within star-forming regions. Aims. Our aim is to identify the dominant molecular cooling lines and characteristic emission features in the 1.3 mm window of distinct regions in the northern part of the Orion A molecular cloud. By defining and analysing template regions, we also intend to help with the interpretation of observations from more distant sources which cannot be easily spatially resolved. Methods. We analyse an imaging line survey covering the area of OMC-1 to OMC-3 from 200.2 to 281.8 GHz obtained with the PI230 receiver at the APEX telescope. Masks are used to define regions with distinct properties (e.g. column density or temperature ranges) from which we obtain averaged spectra. Lines of 29 molecular species (55 isotopologues) are fitted for each region to obtain the respective total intensity. Results. We find that strong sources like Orion KL have a clear impact on the emission on larger scales. Although not spatially extended, their line emission contributes substantially to spectra averaged over large regions. Conversely, the emission signatures of dense, cold regions like OMC-2 and OMC-3 (e.g. enhanced N2H+ emission and low HCN/HNC ratio) seem to be difficult to pick up on larger scales, where they are eclipsed by signatures of stronger sources. In all regions, HCO+ appears to contribute between 3 and 6% to the total intensity, the most stable value for all bright species. N2H+ shows the strongest correlation with column density, but not with typical high-density tracers like HCN, HCO+, H2CO, or HNC. Common line ratios associated with UV illumination, CN/HNC and CN/HCO+, show ambiguous results on larger scales, suggesting that the identification of UV illuminated material may be more challenging. The HCN/HNC ratio may be related to temperature over varying scales.

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35

Chatzichristou, Eleni T. "Mapping the Dynamics of the Quasar 3C 48." Symposium - International Astronomical Union 205 (2001): 162–65. http://dx.doi.org/10.1017/s0074180900220834.

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The archetypical, nearby (z=0.37) quasar 3C 48 is an unusual CSS radio source with excess far-IR emission, whose one-sided radio jet is aligned with the extended ionized emission and a putative second nucleus. Because of its high AGN luminosity and proximity, 3C 48 is a good candidate to search for kinematic signatures of the radio jet-gas coupling and/or of a recent interaction. The radio morphology and our ground-based integral field spectroscopy suggest that the jet is interacting with its immediate environment. Using STIS aboard HST in several slit positions within the central 1”, we map the kinematics and physical conditions of the extended emission line gas and their relations to near-nuclear star forming regions found in existing HST images.

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36

Hadzhiyska, Boryana, Sandro Tacchella, Sownak Bose, and Daniel J. Eisenstein. "The galaxy–halo connection of emission-line galaxies in IllustrisTNG." Monthly Notices of the Royal Astronomical Society 502, no. 3 (January 30, 2021): 3599–617. http://dx.doi.org/10.1093/mnras/stab243.

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ABSTRACT We employ the hydrodynamical simulation IllustrisTNG-300-1 to explore the halo occupation distribution (HOD) and environmental dependence of luminous star-forming emission-line galaxies (ELGs) at z ∼ 1. Such galaxies are key targets for current and upcoming cosmological surveys. We select model galaxies through cuts in colour–colour space allowing for a direct comparison with the Extended Baryon Oscillation Spectroscopic Survey and the Dark Energy Spectroscopic Instrument (DESI) surveys and then compare them with galaxies selected based on specific star formation rate (sSFR) and stellar mass. We demonstrate that the ELG populations are twice more likely to reside in lower density regions (sheets) compared with the mass-selected populations and twice less likely to occupy the densest regions of the cosmic web (knots). We also show that the colour-selected and sSFR-selected ELGs exhibit very similar occupation and clustering statistics, finding that the agreement is best for lower redshifts. In contrast with the mass-selected sample, the occupation of haloes by a central ELG peaks at ∼20 per cent. We furthermore explore the dependence of the HOD and the autocorrelation on environment, noticing that at fixed halo mass, galaxies in high-density regions cluster about 10 times more strongly than low-density ones. This result suggests that we should model carefully the galaxy–halo relation and implement assembly bias effects into our models (estimated at ∼4 per cent of the clustering of the DESI colour-selected sample at z = 0.8). Finally, we apply a simple mock recipe to recover the clustering on large scales (r ≳ 1 Mpc h−1) to within 1 per cent by augmenting the HOD model with an environment dependence, demonstrating the power of adopting flexible population models.

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37

Claeyssens, A., J. Richard, J. Blaizot, T. Garel, F. Leclercq, V. Patrício, A. Verhamme, et al. "Spectral variations of Lyman $\alpha$ emission within strongly lensed sources observed with MUSE." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 10, 2019): 5022–29. http://dx.doi.org/10.1093/mnras/stz2492.

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ABSTRACT We present an analysis of ${\rm H\,\rm{\small {I}}}$ Lyman $\alpha$ emission in deep VLT/MUSE observations of two highly magnified and extended galaxies at $z=3.5$ and 4.03, including a newly discovered, almost complete Einstein ring. While these Lyman $\alpha$ haloes are intrinsically similar to the ones typically seen in other MUSE deep fields, the benefits of gravitational lensing allow us to construct exceptionally detailed maps of Lyman $\alpha$ line properties at sub-kpc scales. By combining all multiple images, we are able to observe complex structures in the Lyman $\alpha$ emission and uncover small ($\sim120$ km s−1 in Lyman $\alpha$ peak shift), but significant at $ \gt $4 $\sigma$, systematic variations in the shape of the Lyman $\alpha$ line profile within each halo. Indeed, we observe a global trend for the line peak shift to become redder at large radii, together with a strong correlation between the peak wavelength and line width. This systematic intrahalo variation is markedly similar to the object-to-object variations obtained from the integrated properties of recent large samples. Regions of high surface brightness correspond to relatively small line shifts, which could indicate that Lyman $\alpha$ emission escapes preferentially from regions where the line profile has been less severely affected by scattering of Lyman $\alpha$ photons.

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38

Balmaverde, B., A. Capetti, A. Marconi, G. Venturi, M. Chiaberge, R. D. Baldi, S. Baum, et al. "The MURALES survey." Astronomy & Astrophysics 632 (December 2019): A124. http://dx.doi.org/10.1051/0004-6361/201935544.

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We present observations of a complete sub-sample of 20 radio galaxies from the Third Cambridge Catalog (3C) with redshift < 0.3 obtained from VLT/MUSE optical integral field spectrograph. These data have been obtained as part of the survey MURALES (a MUse RAdio Loud Emission line Snapshot survey) with the main goal of exploring the active galactic nuclei (AGN) feedback process in a sizeable sample of the most powerful radio sources at low redshift. We present the data analysis and, for each source, the resulting emission line images and the 2D gas velocity field. Thanks to their unprecedented depth (the median 3σ surface brightness limit in the emission line maps is 6 × 10−18 erg s−1 cm−2 arcsec−2), these observations reveal emission line structures extending to several tens of kiloparsec in most objects. In nine sources the gas velocity shows ordered rotation, but in the other cases it is highly complex. 3C sources show a connection between radio morphology and emission line properties. Whereas, in three of the four Fanaroff and Riley Class I radio galaxies (FR Is), the line emission regions are compact, ∼1 kpc in size; in all but one of the Class II radiogalaxies FR IIs, we detected large scale structures of ionized gas with a median extent of 17 kpc. Among the FR IIs, those of high and low excitation show extended gas structures with similar morphological properties, suggesting that they both inhabit regions characterized by a rich gaseous environment on kpc scale.

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39

Rodriguez, Luis F. "H Atom Observations in Near-Stellar Environments." Symposium - International Astronomical Union 150 (1992): 351–55. http://dx.doi.org/10.1017/s0074180900090355.

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Interferometric observations of the 21-cm line of atomic hydrogen resolve out the emission from extended, line-of-sight clouds and allow the detailed study of compact H I structures in the surroundings of some stars. These atomic hydrogen components most probably are the result of photodissociation of gas that originally was in molecular form. They have been observed in H II regions, reflection nebulae, and planetary nebulae. The study of this atomic hydrogen component is important to determine the mass and physical conditions of gas in the environment of luminous stars and to test our theoretical knowledge of photodissociation regions.

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40

Goicoechea, Javier R., François Lique, and Miriam G. Santa-Maria. "Anomalous HCN emission from warm giant molecular clouds." Astronomy & Astrophysics 658 (January 27, 2022): A28. http://dx.doi.org/10.1051/0004-6361/202142210.

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Hydrogen cyanide (HCN) is considered a good tracer of the dense molecular gas that serves as fuel for star formation. However, recent large-scale surveys of giant molecular clouds (GMCs) have detected extended HCN rotational line emission far from star-forming cores. Such observations often spectroscopically resolve the HCN J = 1–0 (partially also the J = 2–1 and 3–2) hyperfine structure (HFS). A precise determination of the physical conditions of the gas requires treating the HFS line overlap effects. Here, we study the HCN HFS excitation and line emission using nonlocal radiative transfer models that include line overlaps and new HFS-resolved collisional rate coefficients for inelastic collisions of HCN with both para-H2 and ortho-H2 (computed via the scaled-infinite order sudden approximation up to Tk = 500 K). In addition, we account for the role of electron collisions in the HFS level excitation. We find that line overlap and opacity effects frequently produce anomalous HCN J = 1–0 HFS line intensity ratios (i.e., inconsistent with the common assumption of the same Tex for all HFS lines) as well as anomalous HFS line width ratios. Line overlap and electron collisions also enhance the excitation of the higher J rotational lines. Our models explain the anomalous HCN J = 1–0 HFS spectra observed in the Orion Bar and Horsehead photodissociation regions. As shown in previous studies, electron excitation becomes important for molecular gas with H2 densities below a few 105 cm−3 and electron abundances above ~10−5. We find that when electron collisions are dominant, the relative intensities of the HCN J = 1–0 HFS lines can be anomalous too. In particular, electron excitation can produce low-surface-brightness HCN emission from very extended but low-density gas in GMCs. The existence of such a widespread HCN emission component may affect the interpretation of the extragalactic relationship HCN luminosity versus star-formation rate. Alternatively, extended HCN emission may arise from dense star-forming cores and become resonantly scattered by large envelopes of lower density gas. There are two scenarios – namely, electron-assisted (weakly) collisionally excited versus scattering – that lead to different HCN J = 1–0 HFS intensity ratios, which can be tested on the basis of observations.

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41

Díaz Trigo, M., D. Petry, E. Humphreys, C. M. V. Impellizzeri, and H. B. Liu. "A search for signatures of interactions of X-ray binary outflows with their environments with ALMA." Astronomy & Astrophysics 650 (June 2021): A37. http://dx.doi.org/10.1051/0004-6361/202040160.

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We observed the X-ray binaries Cir X-1, Sco X-1, GRS 1915+105, GX 13+1, and Cyg X-1 with the Atacama Large Millimeter/submillimeter Array (ALMA). Unresolved continuum emission is found at the positions of all the sources at a frequency of 92 GHz, with flux densities ranging between 0.8 and 10 mJy beam−1. In all cases the emission can be associated with jets that have been extensively observed at lower frequencies. We searched for line emission from Hα recombination, SiO, H2O, and CH3OH at the positions of all the sources and, for Cir X-1 and Cyg X-1, also at regions where shocks associated with an interaction between the jet and the interstellar medium had previously been observed. The search did not yield any significant detection, resulting in 3σ upper limits between 0.65 and 3.7 K km s−1 for the existence of line emission in these regions. In contrast, we detected spatially unresolved SiO emission in the field of view of GX 13+1, and we tentatively associate this emission with a SiO maser in a potential young stellar object or evolved star. We also found spatially extended line emission at two additional sites in the field of view of GX 13+1 that we tentatively associate with emission from SO and CH3OH; we speculate that it may be associated with a star-forming region, but again we cannot rule out alternative origins such as emission from evolved stars.

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42

Whiteoak, J. B., and J. D. Bunton. "FST Observations of NGC 4945 and the Circinus Galaxy." Publications of the Astronomical Society of Australia 6, no. 2 (1985): 171–74. http://dx.doi.org/10.1017/s1323358000018014.

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AbstractThe Fleurs synthesis telescope, which provides 20 arcsec resolution at 1.4 GHz, was used to map the continuum emission in NGC 4945 and the Circinus galaxy. Both objects have prominent small-diameter radio nuclei, containing 50% to 75% of the total intensity, superimposed on extended emission associated with the outer regions of the galaxies. The scale of the nuclei, together with the large velocity widths of the associated spectral-line profiles, are not unlike those encountered in the central region of the Galaxy.

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43

Allen, M. G., M. A. Dopita, and Z. I. Tsvetanov. "Excitation Mechanisms in Seyfert Galaxies." International Astronomical Union Colloquium 159 (1997): 392–93. http://dx.doi.org/10.1017/s0252921100040550.

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The excitation mechanism of the extended emission-line regions (EELRs) in Seyfert galaxies is commonly thought to be nuclear photoionization. However, some Seyfert galaxies have EELRs with disturbed kinematics, outflows, and morphology which is indicative of interaction between radio plasma and the ISM of the host galaxy. In these cases shock excitation must also be considered (BickneU 1993).To investigate the importance of shocks and photoionization, we have taken two approaches: mapping the spatial dependence of the line ratios, and using UV line ratios which are sensitive discriminants between shocks and photoionization.

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44

Long, Feng, Sean M. Andrews, Giovanni Rosotti, Daniel Harsono, Paola Pinilla, David J. Wilner, Karin I. Öberg, Richard Teague, Leon Trapman, and Benoît Tabone. "Gas Disk Sizes from CO Line Observations: A Test of Angular Momentum Evolution." Astrophysical Journal 931, no. 1 (May 1, 2022): 6. http://dx.doi.org/10.3847/1538-4357/ac634e.

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Abstract The size of a disk encodes important information about its evolution. Combining new Submillimeter Array observations with archival Atacama Large Millimeter/submillimeter Array data, we analyze millimeter continuum and CO emission line sizes for a sample of 44 protoplanetary disks around stars with masses of 0.15–2 M ⊙ in several nearby star-forming regions. Sizes measured from 12CO line emission span from 50 to 1000 au. This range could be explained by viscous evolution models with different α values (mostly of 10−4–10−3) and/or a spread of initial conditions. The CO sizes for most disks are also consistent with MHD wind models that directly remove disk angular momentum, but very large initial disk sizes would be required to account for the very extended CO disks in the sample. As no CO size evolution is observed across stellar ages of 0.5–20 Myr in this sample, determining the dominant mechanism of disk evolution will require a more complete sample for both younger and more evolved systems. We find that the CO emission is universally more extended than the continuum emission by an average factor of 2.9 ± 1.2. The ratio of the CO to continuum sizes does not show any trend with stellar mass, millimeter continuum luminosity, or the properties of substructures. The GO Tau disk has the most extended CO emission in this sample, with an extreme CO-to-continuum size ratio of 7.6. Seven additional disks in the sample show high size ratios (≳4) that we interpret as clear signs of substantial radial drift.

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45

Pogge, R. W., and M. M. Derobertis. "Subarcsecond-Scale Optical and Radio Structure Correlations in Seyfert Galaxies." Symposium - International Astronomical Union 159 (1994): 455. http://dx.doi.org/10.1017/s0074180900176363.

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An unanswered question in the study of Seyferts is the nature of the relationship between the extended radio-continuum and optical emission-line gas. Detailed comparison is difficult as most Seyferts have radio structure on sub-arcsecond scales, while most optical imaging is on 1–2″ scales. Despite this, some basic features have emerged. Extended radio and optical emission regions are generally aligned in projection, but the overall optical emission extends to much greater galactocentric radii. Pedlar et al. (1989) and Whittle et al. (1986) have reported a tendency for optical emission knots to lie behind the radio lobes, interpreted in terms of the “cooling length” of gas heated by a radiative bowshock driven into the ISM by a jet. In NGC 1068 (Cecil et al. 1990) and M51 (Cecil 1988), however, ambient gas appears to be piling up ahead of a radio lobe at the terminus of the radio jet.

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46

Yadav, Jyoti, Mousumi Das, Sudhanshu Barway, and Francoise Combes. "A triple active galactic nucleus in the NGC 7733–7734 merging group." Astronomy & Astrophysics 651 (July 2021): L9. http://dx.doi.org/10.1051/0004-6361/202141210.

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Context. Galaxy interactions and mergers can lead to supermassive black hole (SMBH) binaries, which become active galactic nucleus (AGN) pairs when the SMBHs start accreting mass. If there is a third galaxy involved in the interaction, then a triple-AGN system can form. Aims. Our goal is to investigate the nature of the nuclear emission from the galaxies in the interacting pair NGC 7733–NGC 7734 using archival VLT/MUSE integral field spectrograph data and study its relation to the stellar mass distribution traced by near-infrared (NIR) observations from the South African Astronomical Observatory (SAAO). Methods. We conducted NIR observations using the SAAO and identified the morphological properties of bulges in each galaxy. We used MUSE data to obtain a set of ionized emission lines from each galaxy and studied the ionization mechanism. We also examined the relation of the galaxy pair with any nearby companions with far-ultraviolet observations using the UVIT. Results. The emission line analysis from the central regions of NGC 7733 and NGC 7734 shows Seyfert and low ionization nuclear emission-line regions type AGN activity. The galaxy pair NGC 7733−34 also shows evidence of a third component, which has Seyfert-like emission. Hence, the galaxy pair NGC 7733−34 forms a triple-AGN system. We also detected an extended narrow-line region associated with the nucleus of NGC 7733.

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47

Parkash, Vaishali, Michael J. I. Brown, T. H. Jarrett, A. Fraser-McKelvie, and M. E. Cluver. "H i galaxies with little star formation: an abundance of LIERs." Monthly Notices of the Royal Astronomical Society 485, no. 3 (March 2, 2019): 3169–84. http://dx.doi.org/10.1093/mnras/stz593.

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Abstract We present a sample of 91 H i galaxies with little or no star formation, and discuss the analysis of the integral field unit (IFU) spectra of 28 of these galaxies. We identified H i galaxies from the H i Parkes All-Sky Survey Catalog (HICAT) with Wide-field Infrared Survey Explorer (WISE) colours consistent with low specific star formation (<10−10.4 yr−1), and obtained optical IFU spectra with the Wide-Field Spectrograph (WiFeS). Visual inspection of the PanSTARRS, Dark Energy Survey, and Carnegie-Irvine imaging of 62 galaxies reveals that at least 32 galaxies in the sample have low levels of star formation, primarily in arms/rings. New IFU spectra of 28 of these galaxies reveals 3 galaxies with central star formation, 1 galaxy with low-ionization nuclear emission-line regions (LINERs), 20 with extended low-ionization emission-line regions (LIERs), and 4 with high excitation Seyfert (Sy) emission. From the spectroscopic analysis of H i selected galaxies with little star formation, we conclude that 75 per cent of this population are LINERs/LIERs.

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48

Weber, Michael L., Barbara Ercolano, Giovanni Picogna, Lee Hartmann, and Peter J. Rodenkirch. "The interpretation of protoplanetary disc wind diagnostic lines from X-ray photoevaporation and analytical MHD models." Monthly Notices of the Royal Astronomical Society 496, no. 1 (June 3, 2020): 223–44. http://dx.doi.org/10.1093/mnras/staa1549.

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ABSTRACT High-resolution spectra of typical wind diagnostics ([O i] 6300 Å and other forbidden emission lines) can often be decomposed into multiple components: high-velocity components with blueshifts up to several 100 km s−1 are usually attributed to fast jets, while narrow (NLVC) and broad (BLVC) low-velocity components are believed to trace slower disc winds. Under the assumption that the line broadening is dominated by Keplerian rotation, several studies have found that the BLVCs should trace gas launched between 0.05 and 0.5 au and correlations between the properties of BLVCs and NLVCs have been interpreted as evidence for the emission tracing an extended magnetohydrodynamics (MHD) wind and not a photoevaporative wind. We calculated synthetic line profiles obtained from detailed photoionization calculations of an X-ray photoevaporation model and a simple MHD wind model and analysed the emission regions of different diagnostic lines and the resulting spectral profiles. The photoevaporation model reproduces most of the observed NLVCs but not the BLVCs or HVCs. The MHD model is able to reproduce all components but produces Keplerian double peaks at average inclinations that are rarely observed. The combination of MHD and photoevaporative winds could solve this problem. Our results suggest that the Gaussian decomposition does not allow for a clear distinction of flux from different wind regions and that the line broadening is often dominated by the velocity gradient in the outflow rather than by Keplerian rotation. We show that observed correlations between BLVC and NLVC do not necessarily imply a common origin in an extended MHD wind.

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49

Wilson, Andrew S. "The Narrow-Line Regions of Seyfert and Radio Galaxies." International Astronomical Union Colloquium 159 (1997): 264–79. http://dx.doi.org/10.1017/s0252921100040276.

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AbstractThis paper reviews the morphology, excitation, and ionization of the gas in the narrow and extended narrow line regions (NLRs and ENLRs) in AGNs. Many high-resolution images of the NLRs of Seyfert galaxies are now available from HST. In some galaxies, these images reveal straight, sharp-edged V-shaped structures (believed to be the projections of 3-dimensional cones), while in others there is a close association between the ionized gas and the radio components. The latter effect arises through radiative shocks driven into the surrounding interstellar gas by the outwardly moving radio components or jets. Photoionization models of ionization-bounded clouds are quite successful in reproducing the line intensity ratios, but a number of problems remain. These problems may be resolved if matter-bounded clouds are also present. Differences between the excitation levels of different NLRs and ENLRs may reflect variations in the fraction of matter-bounded clouds as well as variations in the ionization parameter. I discuss the issue of whether the radiation responsible for photoionizing the gas in Seyfert 2 galaxies originates from a hidden, compact type 1 Seyfert nucleus or from photoionizing shocks within the NLR. These two scenarios are hard to distinguish between. The photoionizing-shock model requires surprisingly high pre-shock densities, raising the question of whether the shocks are sufficiently energetic to power the observed line emission.

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50

Pabst, C. H. M., J. R. Goicoechea, A. Hacar, D. Teyssier, O. Berné, M. G. Wolfire, R. D. Higgins та ін. "[C II] 158 μm line emission from Orion A". Astronomy & Astrophysics 658 (лютий 2022): A98. http://dx.doi.org/10.1051/0004-6361/202140805.

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Context. The [C II] 158 μm fine-structure line is the dominant cooling line of moderate-density photodissociation regions (PDRs) illuminated by moderately bright far-ultraviolet (FUV) radiation fields. This makes this line a prime diagnostic for extended regions illuminated by massive stars. Aims. We aim to understand the origin of [C II] emission and its relation to other tracers of gas and dust in PDRs. One focus is a study of the heating efficiency of interstellar gas as traced by the [C II] line to test models of the photoelectric heating of neutral gas by polycyclic aromatic hydrocarbon (PAH) molecules and very small grains. Methods. We make use of a one-square-degree map of velocity-resolved [C II] line emission toward the Orion Nebula complex, and split this out into the individual spatial components, the expanding Veil Shell, the surface of OMC4, and the PDRs associated with the compact H II region of M43 and the reflection nebula NGC 1977. We employed Herschel far-infrared photometric images to determine dust properties. Moreover, we compared with Spitzer mid-infrared photometry to trace hot dust and large molecules, and velocity-resolved IRAM 30m CO(2–1) observations of the molecular gas. Results. The [C II] intensity is tightly correlated with PAH emission in the IRAC 8 μm band and far-infrared emission from warm dust, with small variations between the four studied subregions (Veil Shell, OMC4, M43, and NGC 1977). The correlation between [C II] and CO(2-1) is very different in the four subregions and is very sensitive to the detailed geometry of the respective regions. Constant-density PDR models are able to reproduce the observed [C II], CO(2–1), and integrated far-infrared (FIR) intensities. The physical conditions in the Veil Shell of the Orion Nebula, M43, and NGC 1977 reveal a constant ratio of thermal pressure pth over incident FUV radiation field measured by G0. We observe strong variations in the photoelectric heating efficiency in the Veil Shell behind the Orion Bar and these variations are seemingly not related to the spectral properties of the PAHs. Conclusions. The [C II] emission from the Orion Nebula complex stems mainly from moderately illuminated PDR surfaces. The correlations of the different tracers ([C II], FIR, CO, 70 μm, and 8 μm emission) show small variations that are not yet understood. Future observations with the James Webb Space Telescope can shine light on the PAH properties that may be linked to these variations.

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