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Artículos de revistas sobre el tema "NGC 4945"

Autor: Grafiati

Publicado: 10 de marzo de 2023

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1

Tang, X. D., C. Henkel, K. M. Menten, Y. Gong, S. Martín, S. Mühle, S. Aalto et al. "ALMA view of the 12C/13C isotopic ratio in starburst galaxies". Astronomy & Astrophysics 629 (22 de agosto de 2019): A6. http://dx.doi.org/10.1051/0004-6361/201935603.

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We derive molecular-gas-phase 12C/13C isotope ratios for the central few hundred parsecs of the three nearby starburst galaxies NGC 253, NGC 1068, and NGC 4945 making use of the λ ∼ 3 mm 12CN and 13CN N = 1–0 lines in the ALMA Band 3. The 12C/13C isotopic ratios derived from the ratios of these lines range from 30 to 67 with an average of 41.6 ± 0.2 in NGC 253, from 24 to 62 with an average of 38.3 ± 0.4 in NGC 1068, and from 6 to 44 with an average of 16.9 ± 0.3 in NGC 4945. The highest 12C/13C isotopic ratios are determined in some of the outskirts of the nuclear regions of the three starburst galaxies. The lowest ratios are associated with the northeastern and southwestern molecular peaks of NGC 253, the northeastern and southwestern edge of the mapped region in NGC 1068, and the very center of NGC 4945. In the case of NGC 1068, the measured ratios suggest inflow from the outer part of NGC 1068 into the circum-nuclear disk through both the halo and the bar. Low 12C/13C isotopic ratios in the central regions of these starburst galaxies indicate the presence of highly processed material.

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2

Harnett, Julienne I. "The magnetic fields of NGC 6946 and NGC 4945". Geophysical & Astrophysical Fluid Dynamics 50, n.º 1-3 (enero de 1990): 35–37. http://dx.doi.org/10.1080/03091929008219866.

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3

Koornneef, Jan. "NGC 4945 - A postburst infrared galaxy". Astrophysical Journal 403 (febrero de 1993): 581. http://dx.doi.org/10.1086/172229.

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4

Wang, M., C. Henkel, Y. N. Chin, J. B. Whiteoak, M. Hunt Cunningham y R. Mauersberger. "The Nuclear Starburst in NGC 4945". Highlights of Astronomy 13 (2005): 871. http://dx.doi.org/10.1017/s1539299600017366.

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AbstractNGC 4945 is with D ~3-4 Mpc one of the nearest starburst galaxies known and a goldmine for molecular cloud research. A multi-line mm-wave study has been carried out towards its nuclear region with the Swedish-ESO Sub-millimetre Telescope (SEST). The study covers the frequency range from 82 GHz to 354 GHz and includes 80 transitions of 19 molecules, including rare isotope-bearing species. Applying a Large Velocity Gradient (LVG) code to the data, H2 densities and column densities of 22 molecular species are calculated. Many of these species indicate the presence of a prominent high density interstellar gas component characterized by nH2 ~105cm-3. Abundances of molecular species are calculated and compared with abundances observed toward the starburst galaxies NGC 253 and M 82 and galactic sources. Apparent is an ‘overabundance’ of HNC and CN in the nuclear environment of NGC 4945. NGC 4945 is the second known starburst galaxy with an HNC/HCN abundance ratio ≥1. Carbon, nitrogen, oxygen and sulfur isotope ratios are also determined. The data indicate that high 18O/17O, low 16O/18O and 14N/15N and perhaps also low 32S/34S ratios (6.4±0.3, 195±45, 105±25 and 13.5±2.5, respectively) are characteristic properties of a starburst environment in an advanced evolutionary stage.

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5

Ag�ero, E. L. y G. J. Carranza. "The ionized gas in NGC 4945". Astrophysics and Space Science 121, n.º 2 (1986): 403–11. http://dx.doi.org/10.1007/bf00653711.

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6

McCarthy, Tiege P., Simon P. Ellingsen, Xi Chen, Shari L. Breen, Maxim A. Voronkov y Hai-hua Qiao. "Class I Methanol Maser Emission in NGC 4945". Proceedings of the International Astronomical Union 13, S336 (septiembre de 2017): 105–8. http://dx.doi.org/10.1017/s1743921317010687.

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AbstractWe have detected maser emission from the 36.2 GHz (4−1 → 30E) methanol transition towards NGC 4945. This emission has been observed in two separate epochs and is approximately five orders of magnitude more luminous than typical emission from this transition within our Galaxy. NGC 4945 is only the fourth extragalactic source observed hosting class I methanol maser emission. Extragalactic class I methanol masers do not appear to be simply highly-luminous variants of their galactic counterparts and instead appear to trace large-scale regions where low-velocity shocks are present in molecular gas.

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7

Pérez-Beaupuits, J. P., H. W. W. Spoon, M. Spaans y J. D. Smith. "The deeply obscured AGN of NGC 4945". Astronomy & Astrophysics 533 (26 de agosto de 2011): A56. http://dx.doi.org/10.1051/0004-6361/201117153.

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8

Cunningham, M. R. y J. B. Whiteoak. "The nuclear molecular clouds of NGC 4945". Monthly Notices of the Royal Astronomical Society 364, n.º 1 (21 de noviembre de 2005): 37–46. http://dx.doi.org/10.1111/j.1365-2966.2005.09502.x.

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9

Monje, R. R., S. Lord, E. Falgarone, D. C. Lis, D. A. Neufeld, T. G. Phillips y R. Güsten. "HYDROGEN FLUORIDE TOWARD LUMINOUS NEARBY GALAXIES: NGC 253 AND NGC 4945". Astrophysical Journal 785, n.º 1 (21 de marzo de 2014): 22. http://dx.doi.org/10.1088/0004-637x/785/1/22.

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10

Roy, A. L., T. Oosterloo, W. M. Goss y K. R. Anantharamaiah. "Detection of the H92αrecombination line from NGC 4945". Astronomy and Astrophysics 517 (julio de 2010): A82. http://dx.doi.org/10.1051/0004-6361/200913926.

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11

Marinucci, A., S. Bianchi, G. Fabbiano, G. Matt, G. Risaliti, E. Nardini y J. Wang. "Spatially resolved Fe K spectroscopy of NGC 4945". Monthly Notices of the Royal Astronomical Society 470, n.º 4 (22 de junio de 2017): 4039–47. http://dx.doi.org/10.1093/mnras/stx1551.

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12

McCarthy, T. P., S. P. Ellingsen, S. L. Breen, M. A. Voronkov, X. Chen y H.-h. Qiao. "Variability in extragalactic class I methanol masers: new maser components towards NGC 4945 and NGC 253". Monthly Notices of the Royal Astronomical Society 491, n.º 4 (5 de noviembre de 2019): 4642–55. http://dx.doi.org/10.1093/mnras/stz3098.

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ABSTRACT We have used the Australia Telescope Compact Array (ATCA) to make new observations of the 36.2-GHz (4−1 → 30E) methanol transition towards NGC 4945 and NGC 253. These observations have revealed the presence of new maser components towards these galaxies, and have provided the first clear evidence for variability in extragalactic class I methanol masers. Alongside the new observations of NGC 4945 and NGC 253, we present the results of recent 36.2-GHz methanol maser searches towards 12 galaxies, placing upper limits on the emission from the 36.2-GHz class I transition and the 37.7-GHz (72 → 81E) class II maser line towards these sources. Flux density values for the 7-mm continuum emission towards these sources are also reported where applicable. A re-analysis of the published 36.2-GHz methanol observations of Arp 220 undertaken as part of the search revealed some issues with previous imaging procedures. The re-analysis, combined with non-detections in independent follow-up observations, suggests that there is no 36.2-GHz methanol emission towards Arp 220 stronger than 3.5 mJy in a 10 km s−1 channel (5σ upper limit).

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13

Villicaña-Pedraza, Ilhuiyolitzin, Sergio Martín, Jesus Martín-Pintado, Miguel Requena-Torres, Rolf Guesten, Jairo Armijos, Juan Pablo Pérez-Beaupuits et al. "0.8mm extragalactic surveys of nearby galaxies". Proceedings of the International Astronomical Union 11, S321 (marzo de 2016): 305. http://dx.doi.org/10.1017/s174392131600939x.

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AbstractWe present the first submillimetric line survey of extragalactic sources carried out by APEX. The surveys cover the 0.8 mm atmospheric window from 270 to 370GHz toward NGC253, NGC4945 and Arp220. We found in NGC 253, 150 transitions of 26 molecules. For NGC 4945, 136 transitions of 24 molecules, and 64 transitions of 17 molecules for Arp 220. Column densities and rotation temperatures have been determinate using the Local Thermodinamical Equilibrium(LTE) line profile simulation and fitting in the MADCUBA IJ software. The differences found in ratios between the Galactic Center and the starburst galaxies NGC 4945 and NGC 253 suggest that the gas is less processed in the latter than in the Galactic Center. The high 18O/17O ratios in the galaxies NGC 4945 and NGC 253 suggest also material less processed in the nuclei of these galaxies than in the Galactic Center. This is consistent with the claim that 17O is a more representative primary product than 18O in stellar nucleosynthesis (Wilson and Rood 1994); Also, we did a Multitransitions study of H3O+ at 307GHz, 364GHz, 388GHz and 396GHz. From our non-LTE analysis of H3O+ in NGC253 with RADEX we found that the collisional excitation can not explain the observed intensity of the ortho 396 GHz line. Excitation by radiation from the dust in the Far-IR can roughly explain the observations if the H2 densities are relatively low. From the derived H3O+ column densities we conclude that the chemistry of this molecule is dominated by ionization produce by the starburst in NGC253 (UV radiation from the O stars) and Arp 220 (cosmic rays from the supernovae) and likely from the AGN in NGC4549 (X-rays ); Finally, we report, for the first time, the tentative detection of the molecular ion HCNH+ (precursor of HCN and HNC) toward a galaxy, NGC4945, abundance explain the claimed enhancement of HCN abundance in the AGN, due to the enhancement of the ionization rate by X-rays. The abundance is much larger than the Galactic center of the Milky Way.

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14

Smith, Evan, Rebecca Robles y Eric Perlman. "A QPO in NGC 4945 from Archival RXTE Data". Astrophysical Journal 902, n.º 1 (13 de octubre de 2020): 65. http://dx.doi.org/10.3847/1538-4357/abb593.

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15

Henkel, C., S. Mühle, G. Bendo, G. I. G. Józsa, Y. Gong, S. Viti, S. Aalto et al. "Molecular line emission in NGC 4945, imaged with ALMA". Astronomy & Astrophysics 615 (julio de 2018): A155. http://dx.doi.org/10.1051/0004-6361/201732174.

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NGC 4945 is one of the nearest (D ≈ 3.8 Mpc; 1″ ≈ 19 pc) starburst galaxies. To investigate the structure, dynamics, and composition of the dense nuclear gas of this galaxy, ALMA band 3 (λ ≈ 3−4 mm) observations were carried out with ≈2″ resolution. Three HCN and two HCO+ isotopologues, CS, C3H2, SiO, HCO, and CH3C2H were measured. Spectral line imaging demonstrates the presence of a rotating nuclear disk of projected size 10″ × 2″ reaching out to a galactocentric radius of r ≈ 100 pc with position angle PA = 45° ± 2°, inclination i = 75° ± 2° and an unresolved bright central core of size ≲2″. The continuum source, representing mostly free-free radiation from star forming regions, is more compact than the nuclear disk by a linear factor of two but shows the same position angle and is centered 0.′′39 ± 0.′′14 northeast of the nuclear accretion disk defined by H2O maser emission. Near the systemic velocity but outside the nuclear disk, both HCN J = 1 → 0 and CS J = 2 → 1 delineate molecular arms of length ≳15″ (≳285 pc) on opposite sides of the dynamical center. These are connected by a (deprojected) ≈ 0.6 kpc sized molecular bridge, likely a dense gaseous bar seen almost ends-on, shifting gas from the front and back side into the nuclear disk. Modeling this nuclear disk located farther inside (r ≲100 pc) with tilted rings provides a good fit by inferring a coplanar outflow reaching a characteristic deprojected velocity of ≈50 km s−1. All our molecular lines, with the notable exception of CH3 C2H, show significant absorption near the systemic velocity (≈571 km s−1), within the range ≈500–660 km s−1. Apparently, only molecular transitions with low critical H2 density (ncrit ≲ 104 cm−3) do not show absorption. The velocity field of the nuclear disk, derived from CH3 C2H, provides evidence for rigid rotation in the inner few arcseconds and a dynamical mass of Mtot = (2.1 ± 0.2) × 108 M⊙ inside a galactocentric radius of 2.′′45 (≈45 pc), with a significantly flattened rotation curve farther out. Velocity integrated line intensity maps with most pronounced absorption show molecular peak positions up to ≈1.′′5 (≈30 pc) southwest of the continuum peak, presumably due to absorption, which appears to be most severe slightly northeast of the nuclear maser disk. A nitrogen isotope ratio of 14N/15N ≈ 200–450 is estimated. This range of values is much higher then previously reported on a tentative basis. Therefore, because 15N is less abundant than expected, the question for strong 15N enrichment by massive star ejecta in starbursts still remains to be settled.

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16

Whiteoak, J. B. y J. D. Bunton. "FST Observations of NGC 4945 and the Circinus Galaxy". Publications of the Astronomical Society of Australia 6, n.º 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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17

Whiteoak, J. B. "NGC 4945-A Galaxy with a Nucleus Full of Surprises". Publications of the Astronomical Society of Australia 6, n.º 4 (1986): 467–71. http://dx.doi.org/10.1017/s1323358000018403.

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AbstractAt optical wavelengths NGC 4945 is a nondescript edge-on spiral galaxy, much of which is obscured by dense dust clouds. However, at longer wavelengths a prominent nucleus is exposed which possesses both Seyfert and star-burst characteristics. Microwave observations highlight dense molecular clouds located near the nucleus. The large velocity range of these clouds lacks an adequate interpretation.

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18

Pesce, D. W., J. A. Braatz y C. M. V. Impellizzeri. "SUBMILLIMETER H2O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY". Astrophysical Journal 827, n.º 1 (9 de agosto de 2016): 68. http://dx.doi.org/10.3847/0004-637x/827/1/68.

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19

Emig, Kimberly L., Alberto D. Bolatto, Adam K. Leroy, Elisabeth A. C. Mills, María J. Jiménez Donaire, Alexander G. G. M. Tielens, Adam Ginsburg et al. "Super Star Clusters in the Central Starburst of NGC 4945". Astrophysical Journal 903, n.º 1 (30 de octubre de 2020): 50. http://dx.doi.org/10.3847/1538-4357/abb67d.

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20

Bolatto, Alberto D., Adam K. Leroy, Rebecca C. Levy, David S. Meier, Elisabeth A. C. Mills, Todd A. Thompson, Kimberly L. Emig et al. "ALMA Imaging of a Galactic Molecular Outflow in NGC 4945". Astrophysical Journal 923, n.º 1 (1 de diciembre de 2021): 83. http://dx.doi.org/10.3847/1538-4357/ac2c08.

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Abstract We present the ALMA detection of molecular outflowing gas in the central regions of NGC 4945, one of the nearest starbursts and also one of the nearest hosts of an active galactic nucleus (AGN). We detect four outflow plumes in CO J = 3 − 2 at ∼0.″3 resolution that appear to correspond to molecular gas located near the edges of the known ionized outflow cone and its (unobserved) counterpart behind the disk. The fastest and brightest of these plumes has emission reaching observed line-of-sight projected velocities of over 450 km s−1 beyond systemic, equivalent to an estimated physical outflow velocity v ≳ 600 km s−1 for the fastest emission. Most of these plumes have corresponding emission in HCN or HCO+ J = 4 − 3. We discuss a kinematic model for the outflow emission where the molecular gas has the geometry of the ionized gas cone and shares the rotation velocity of the galaxy when ejected. We use this model to explain the velocities we observe, constrain the physical speed of the ejected material, and account for the fraction of outflowing gas that is not detected due to confusion with the galaxy disk. We estimate a total molecular mass outflow rate M ̇ mol ∼ 20 M ⊙ yr−1 flowing through a surface within 100 pc of the disk midplane, likely driven by a combination of the central starburst and AGN.

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21

Chou, Richard C. Y., A. B. Peck, J. Lim, S. Matsushita, S. Muller, S. Sawada‐Satoh, Dinh‐V‐Trung, F. Boone y C. Henkel. "The Circumnuclear Molecular Gas in the Seyfert Galaxy NGC 4945". Astrophysical Journal 670, n.º 1 (20 de noviembre de 2007): 116–28. http://dx.doi.org/10.1086/521351.

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22

Done, C., G. M. Madejski y D. A. Smith. "NGC 4945: The Brightest Seyfert 2 Galaxy at 100 keV". Astrophysical Journal 463, n.º 2 (1 de junio de 1996): L63—L66. http://dx.doi.org/10.1086/310056.

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23

Ghosh, S. K., R. S. Bisht, K. V. K. Iyengar, T. N. Rengarajan, S. N. Tandon y R. P. Verma. "Far-infrared observations of NGC 4945 and the Circinus galaxy". Astrophysical Journal 391 (mayo de 1992): 111. http://dx.doi.org/10.1086/171328.

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24

Curran, S. J., L. E. B. Johansson, P. Bergman, A. Heikkilä y S. Aalto. "Molecular gas conditions in NGC 4945 and the Circinus galaxy". Astronomy & Astrophysics 367, n.º 2 (febrero de 2001): 457–69. http://dx.doi.org/10.1051/0004-6361:20000462.

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25

Ott, M., J. B. Whiteoak, C. Henkel y R. Wielebinski. "Atomic and molecular gas in the starburst galaxy NGC 4945". Astronomy & Astrophysics 372, n.º 2 (junio de 2001): 463–76. http://dx.doi.org/10.1051/0004-6361:20010505.

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26

McCarthy, T. P., S. P. Ellingsen, S. L. Breen, C. Henkel, M. A. Voronkov y X. Chen. "Investigations of the Class I methanol masers in NGC 4945". Monthly Notices of the Royal Astronomical Society 480, n.º 4 (9 de agosto de 2018): 4578–88. http://dx.doi.org/10.1093/mnras/sty2192.

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27

Humphreys, E. M. L., W. H. T. Vlemmings, C. M. V. Impellizzeri, M. Galametz, M. Olberg, J. E. Conway, V. Belitsky y C. De Breuck. "Detection of 183 GHz H2O megamaser emission towards NGC 4945". Astronomy & Astrophysics 592 (agosto de 2016): L13. http://dx.doi.org/10.1051/0004-6361/201629168.

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28

Moorwood, A. F. M. y E. Olivia. "Extended infrared line emission excited by starburst and Seyfert activity in NGC 3256 and NGC 4945". Astrophysical Journal 429 (julio de 1994): 602. http://dx.doi.org/10.1086/174347.

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29

Hitschfeld, M., M. Aravena, C. Kramer, F. Bertoldi y J. Stutzki. "Atomic carbon abundance at the centers of NGC 4945 and circinus". EAS Publications Series 31 (2008): 177–78. http://dx.doi.org/10.1051/eas:0831035.

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30

Humire, P. K., C. Henkel, Y. Gong, S. Leurini, R. Mauersberger, S. A. Levshakov, B. Winkel et al. "36 GHz methanol lines from nearby galaxies: maser or quasi-thermal emission?" Astronomy & Astrophysics 633 (enero de 2020): A106. http://dx.doi.org/10.1051/0004-6361/201936330.

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Methanol (CH3OH) is one of the most abundant interstellar molecules, offering a vast number of transitions to be studied, including many maser lines. However, while the strongest Galactic CH3OH lines, the so-called class II masers, show no indications for the presence of superluminous counterparts in external galaxies, the less luminous Galactic class I sources appear to be different. Here we report class I 36 GHz (λ ≈ 0.8 cm) CH3OH 4−1 → 30 E line emission from the nearby galaxies Maffei 2 (D ≈ 6 Mpc) and IC 342 (D ≈ 3.5 Mpc), measured with the 100 m telescope at Effelsberg at three different epochs within a time span of about five weeks. The 36 GHz methanol line of Maffei 2 is the second most luminous among the sources detected with certainty outside the Local Group of galaxies. This is not matched by the moderate infrared luminosity of Maffei 2. Higher-resolution data are required to check whether this is related to its prominent bar and associated shocks. Upper limits for M 82, NGC 4388, NGC 5728 and Arp 220 are also presented. The previously reported detection of 36 GHz maser emission in Arp 220 is not confirmed. Nondetections are reported from the related class I 44 GHz (λ ≈ 0.7 cm) methanol transition towards Maffei 2 and IC 342, indicating that this line is not stronger than its 36 GHz counterpart. In contrast to the previously detected 36 GHz CH3OH emission in NGC 253 and NGC 4945, our 36 GHz profiles towards Maffei 2 and IC 342 are similar to those of previously detected nonmasing lines from other molecular species. However, by analogy to our Galactic center region, it may well be possible that the 36 GHz methanol lines in Maffei 2 and IC 342 are composed of a large number of faint and narrow maser features that remain spatially unresolved. In view of this, a search for a weak broad 36 GHz line component would also be desirable in NGC 253 and NGC 4945.

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31

Koribalski, Bärbel, John B. Whiteoak y Sally Houghton. "Peculiar Gas Dynamics in the Starburst Galaxy NGC 253". Publications of the Astronomical Society of Australia 12, n.º 1 (abril de 1995): 20–25. http://dx.doi.org/10.1017/s1323358000019998.

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AbstractHere we present our first results of a study of the neutral hydrogen gas (HI) in the southern spiral galaxy NGC 253 with the Australia Telescope Compact Array. The relative proximity of NGC 253 makes it a very suitable object for detailed studies of large-scale, as well as nuclear, gas dynamics. Several peculiar features have been found. The HI distribution is asymmetric in the outer regions, probably as a result of the strong warping of the spiral arms. A bar associated with the disc, clearly visible in the optical and near-infrared, also reveals its signature in the neutral hydrogen gas. HI absorption measurements reveal unusual motions of the gas in the nuclear region which seem to indicate a fast-rotating ring of cold gas as well as outflow of gas. Similar features have been found in other starburst galaxies, such as M 82, NGC 1808 and NGC 4945, and are interpreted in terms of bar-induced gas dynamics and star formation.

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32

Requena-Torres, M. A., R. Güsten, J. Martín-Pintado, S. Martín, R. Aladro, A. Weiss, S. Heyminck y B. Klein. "Chemical Complexity in Extragalactic Nuclei: ARP 220, NGC 253 and NGC 4945 surveys with the APEX telescope". EAS Publications Series 52 (2011): 299–300. http://dx.doi.org/10.1051/eas/1152056.

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33

Harnett, J. I., R. F. Haynes, R. Wielebinski y U. Klein. "Radio Polarization Observations of Three Southern Galaxies". Publications of the Astronomical Society of Australia 8, n.º 3 (1990): 257–60. http://dx.doi.org/10.1017/s1323358000023468.

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AbstractObservations of polarized emission and consequently the investigation of magnetic fields in northern galaxies, have been conducted successfully for some time with, for example, the 100-m Effelsberg telescope of the Max-Planck-Institut-für Radioastronomie and the VLA. However, the opportunity to make corresponding studies in the southern hemisphere has only recently become possible. Therefore, we have begun a long-range project aimed at studying the morphology and dynamics of southern galaxies using the facilities of the Parkes and Molonglo radio telescopes, the Siding Spring optical facilities and the Australia Telescope. Here we present preliminary results from Parkes observations of the three well known galaxies: NGC 253, NGC 4945 and M 83.

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34

Harnett, J. I., U. Klein, R. Wielebinski y R. F. Haynes. "The Distribution of Radio Polarisation in Three Southern Galaxies". Publications of the Astronomical Society of Australia 9, n.º 2 (1991): 266–68. http://dx.doi.org/10.1017/s1323358000024073.

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AbstractWe are studying the distribution and morphology of magnetic fields in southern face-on and edge-on galaxies with the intention of clarifying the distribution, lifetimes and transport mechanisms of cosmic rays, and investigating the intensity and orientation of the disc, halo and poloidal magnetic fields. As a preliminary study, before the Australia Telescope was available, we observed a sample of well-known southern spiral galaxies with the Parkes radio telescope.Here, we present the resulting polarisation images for three galaxies, NGC 253, M 83 and NGC 4945, which were observed at 4.75 GHz and 8.55 GHz. The corresponding total power contour plots have been already published by Harnett et al. (1989a, 1990).

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35

McCarthy, Tiege P., Simon P. Ellingsen, Xi Chen, Shari L. Breen, Maxim A. Voronkov y Hai-hua Qiao. "Detection of 36 GHz Class I Methanol Maser Emission toward NGC 4945". Astrophysical Journal 846, n.º 2 (13 de septiembre de 2017): 156. http://dx.doi.org/10.3847/1538-4357/aa872c.

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36

Elmouttie, M., R. F. Haynes, K. L. Jones, M. Ehle, R. Beck, J. I. Harnett y R. Wielebinski. "The radio continuum structure of the edge-on spiral galaxy NGC 4945". Monthly Notices of the Royal Astronomical Society 284, n.º 4 (1 de febrero de 1997): 830–38. http://dx.doi.org/10.1093/mnras/284.4.830.

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37

Chen, Yang y Jie-Hao Huang. "The Conelike Hα Nebula in NGC 4945: A Galactic Superwind Bow Shock?" Astrophysical Journal 479, n.º 1 (10 de abril de 1997): L23—L26. http://dx.doi.org/10.1086/310582.

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38

Puccetti, Simonetta, Andrea Comastri, Fabrizio Fiore, Patricia Arévalo, Guido Risaliti, Franz E. Bauer, William N. Brandt et al. "THE VARIABLE HARD X-RAY EMISSION OF NGC 4945 AS OBSERVED BYNUSTAR". Astrophysical Journal 793, n.º 1 (2 de septiembre de 2014): 26. http://dx.doi.org/10.1088/0004-637x/793/1/26.

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39

Hunt, Maria R. y John B. Whiteoak. "High-Resolution Acta Observations of the Circumnuclear Molecular Clouds of Ngc 4945". Astrophysics and Space Science 295, n.º 1-2 (enero de 2005): 257–62. http://dx.doi.org/10.1007/s10509-005-3701-2.

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40

Spoon, H. W. W., A. F. M. Moorwood, K. M. Pontoppidan, J. Cami, M. Kregel, D. Lutz y A. G. G. M. Tielens. "Detection of strongly processed ice in the central starburst of NGC 4945". Astronomy & Astrophysics 402, n.º 2 (14 de abril de 2003): 499–507. http://dx.doi.org/10.1051/0004-6361:20030290.

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41

Yaqoob, Tahir. "The nature of the Compton-thick X-ray reprocessor in NGC 4945". Monthly Notices of the Royal Astronomical Society 423, n.º 4 (1 de junio de 2012): 3360–96. http://dx.doi.org/10.1111/j.1365-2966.2012.21129.x.

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42

Lipari, Sebastian, Zlatan Tsvetanov y F. Macchetto. "Luminous Infrared Galaxies. II. NGC 4945: A Nearby Obscured Starburst/Seyfert Nucleus". Astrophysical Journal Supplement Series 111, n.º 2 (agosto de 1997): 369–75. http://dx.doi.org/10.1086/313019.

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43

Madejski, G., Ch Done y P. Zycki. "Black holes in AGN: recent results on IC 4329a and NGC 4945". Astronomische Nachrichten 320, n.º 4-5 (agosto de 1999): 240–43. http://dx.doi.org/10.1002/1521-3994(199908)320:4/5<240::aid-asna240>3.0.co;2-f.

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44

Moran, J. M. "H2O Megamasers and Black Holes". Highlights of Astronomy 11, n.º 2 (1998): 956–59. http://dx.doi.org/10.1017/s1539299600019286.

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Resumen

AbstractTwenty-one H2O masers have been identified in the nuclei of active galaxies. The detection rate is about 7 percent. Very Long Baseline Interferometric data of four of these maser systems (NGC 4258, NGC 1068, NGC 4945, and NGC 3079) show evidence of Keplerian disks on a subparsec scale. The best example is NGC 4258. There the masers trace a thin warped disk in nearly perfect circular Keplerian motion. If the apparent thinness is indicative of hydrostatic equilibrium, then the kinetic temperature must be less than 1000K, the magnetic field less than 200 mG, and the mass accretion rate less than about α10-3 M⊙/yr, where a is the viscosity parameter. From direct Zeeman measurements the toroidal magnetic field strength is less than 300 mG. The proper motions of the systemic maser feature imply a distance to the galaxy of 7.3 ± 0.3 Mpc. The high-velocity features show no detectable proper motions or accelerations, which confirms the model of circular Keplerian motion, and puts severe constraints on any alternative model. A feature in the systemic group flared to 20 Jy, offering opportunities to study the physics of the maser emission.

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45

Hagiwara, Yoshiaki, Shinji Horiuchi, Masatoshi Imanishi y Philip G. Edwards. "Second-epoch ALMA Observations of 321 GHz Water Maser Emission in NGC 4945 and the Circinus Galaxy". Astrophysical Journal 923, n.º 2 (1 de diciembre de 2021): 251. http://dx.doi.org/10.3847/1538-4357/ac3089.

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Abstract We present the results of second-epoch ALMA observations of 321 GHz H2O emission toward two nearby active galactic nuclei, NGC 4945 and the Circinus galaxy, together with Tidbinbilla 70 m monitoring of their 22 GHz H2O masers. The two-epoch ALMA observations show that the strengths of the 321 GHz emission are variable by a factor of at least a few, confirming a maser origin. In the second epoch, 321 GHz maser emission from NGC 4945 was not detected, while for the Circinus galaxy the flux density significantly increased and the velocity gradient and dispersion have been measured. With the velocity gradient spanning ∼110 km s−1, we calculate the disk radius to be ∼28 pc, assuming disk rotation around the nucleus. We also estimate the dynamical mass within the central 28 pc to be 4.3 × 108 M ☉, which is significantly larger than the larger-scale dynamical mass, suggesting the velocity gradient does not trace circular motions on that scale. The overall direction of the velocity gradient and velocity range of the blueshifted features are largely consistent with those of the 22 GHz maser emission in a thin disk with smaller radii of 0.1–0.4 pc and molecular outflows within ∼1 pc from the central engine of the galaxy, implying that the 321 GHz masers could trace part of the circumnuclear disk or the nuclear outflows.

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46

Stanghellini, Letizia, Laura Magrini y Viviana Casasola. "GAS-PHASE OXYGEN ABUNDANCES AND RADIAL METALLICITY GRADIENTS IN THE TWO NEARBY SPIRAL GALAXIES NGC 7793 AND NGC 4945". Astrophysical Journal 812, n.º 1 (6 de octubre de 2015): 39. http://dx.doi.org/10.1088/0004-637x/812/1/39.

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47

Itoh, Takeshi, Chris Done, Kazuo Makishima, Grzegorz Madejski, Hisamitsu Awaki, Poshak Gandhi, Naoki Isobe et al. "Suzaku Wide-Band X-Ray Spectroscopy of the Seyfert2 AGN in NGC 4945". Publications of the Astronomical Society of Japan 60, sp1 (20 de febrero de 2008): S251—S261. http://dx.doi.org/10.1093/pasj/60.sp1.s251.

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48

Iwasawa, K., K. Koyama, H. Awaki, H. Kunieda, K. Makishima, T. Tsuru, T. Ohashi y N. Nakai. "X-ray evidence for Seyfert activity buried in the infrared galaxy NGC 4945". Astrophysical Journal 409 (mayo de 1993): 155. http://dx.doi.org/10.1086/172651.

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49

Marinucci, A., G. Risaliti, Junfeng Wang, E. Nardini, M. Elvis, G. Fabbiano, S. Bianchi y G. Matt. "The X-ray reflector in NGC 4945: a time- and space-resolved portrait". Monthly Notices of the Royal Astronomical Society: Letters 423, n.º 1 (11 de abril de 2012): L6—L10. http://dx.doi.org/10.1111/j.1745-3933.2012.01232.x.

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50

Done, Chris, Greg M. Madejski, Piotr T. Życki y Lincoln J. Greenhill. "SimultaneousChandraandRossi X‐Ray Timing ExplorerObservations of the Nearby Bright Seyfert 2 Galaxy NGC 4945". Astrophysical Journal 588, n.º 2 (10 de mayo de 2003): 763–70. http://dx.doi.org/10.1086/374332.

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