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KINEMATICS OF NEARBY ACTIVE
GALACTIC NUCLEUS HOST NGC 7582

Item Type Authors Citation
Electronic Thesis; text Walla, Emily Walla, Emily. (2020). KINEMATICS OF NEARBY ACTIVE GALACTIC NUCLEUS HOST NGC 7582 (Bachelor's thesis, University of Arizona, Tucson, USA).

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KINEMATICS OF NEARBY ACTIVE GALACTIC NUCLEUS HOST NGC 7582
By
EMILY CATHERINE WALLA

____________________

A Thesis Submitted to The Honors College In Partial Fulfillment of the Bachelor’s degree
With Honors in

Astronomy
THE UNIVERSITY OF ARIZONA
MAY 2020

Approved by: ______________________ Dr. Stephanie Juneau NSF National Optical-Infrared Astronomy Research Lab, The Astro Data Lab

Dr. Susan Ridgway, NSF National Optical-Infrared Astronomy Research Laboratory, served as a secondary advisor for this project. She provided extensive scientific background for the project.

Madison Walder, undergraduate student in the University of Arizona Class of Spring 2020, worked on a project adjacent to mine and as such, provided some small modifications to the code eventually used to complete my project.

Leah Fulmer, PhD candidate at the University of Washington, worked with Stephanie Juneau before me and completed some initial analyses and wrote code that was foundational in the first year of the project but was ultimately not implemented in the project’s final form. Building off of Leah’s work has made me better at the python computer language, and their contribution to this project should be recognized.

Draft version May 9, 2020

A

Typeset using L T X default style in AASTeX63
E

Kinematics of Nearby Active Galactic Nucleus Host NGC 7582

Emily Walla,1 Stephanie Juneau,2 Susan Ridgway,2 Madison Walder,1 and Leah Fulmer3

1University of Arizona Department of Astronomy and Steward Observatory
2NSF National Optical-Infrared Astronomy Research Laboratory
3University of Washingtom Department of Astronomy

(Received May 6, 2020; Accepted May 9, 2020)

Submitted to AJ ABSTRACT
High-quality, spatially-resolved spectroscopy from the MUSE instrument on the Very Large Telescope allows for the exploration of the chemical composition and kinematics of stars and gas around Active Galactic Nuclei (AGN). The Galaxy IFU Spectroscopy Tool (GIST) performs kinematic fitting of the MUSE Data, opening the door for analysis of outflows, inflows and structure of active galaxies. We present an analysis, by applying the GIST Pipeline to MUSE IFU data, of the nearby active galaxy NGC 7582. In the star and gas kinematics, we find signatures of a large-scale bar. We report on neutral gas kinematics for the first time, finding tentative evidence for large-scale outflows outside the outflowing ionized gas cones. Furthermore, we confirm the presence of a recently-found kinematically distinct core comprised of a ring of fast-moving stars approximately 600 pc in diameter. Our study emphasizes the need to account for galaxy substructure and different phases of the interstellar medium while continuing to improve our understanding of the connection between AGN and their host galaxies.

Keywords: AGN, galaxy evolution, interstellar medium, neutral gas outflow, ionized gas outflows, galaxy structure, spiral galaxy

1. INTRODUCTION
Active galactic nuclei (AGN) are supermassive black holes at the center of their host galaxies that are actively accreting material and feeding outflows of matter from the galaxy. Through this process of accretion and expulsion, feedback can suppress star formation in some regions of the galaxy while possibly exciting it in others (Cresci et al. 2015). However, the effect AGN have on the long-term evolution of their host galaxy and the role they play in transitioning galaxies from gas-rich with ample star formation to gas-poor with few stellar births are not well understood. Improving the understanding of the AGN-host galaxy relationship requires high-quality observations taken over a wide wavelength range in order to paint the most complete picture possible of the components and kinematics of active galaxies. Itegral-field spectroscopy done by the Multi-Unit Spectroscopic Explorer (MUSE) instrument on the European Southern Observatory’s Very Large Telescope provides approximately 90,000 spatially resolved spectra, allowing for a detailed analysis of the kinematics of gas and stars (Bacon et al. 2010). Furthermore, the MUSE instrument’s wide field of view allows for this kinematic analysis to be done on a kpc scale. Large-scale mapping is vital to understanding the relationship between AGN and their host galaxies, as AGN-ionized regions and outflows often span kpc, and inflows and large-scale structures in the galaxy may not be captured in narrow fields of view. To gain more physical insight on the AGN-host galaxy connection, we conduct a detailed case study of an intriguing active galaxy that has previously showed hints of a relationship between the AGN and the large-scale host galaxy structure. NGC 7582 is a nearby (z = 0.005 (de Vaucouleurs et al. 1991)) galaxy housing a supermassive black hole of mass 5.5 ∗ 107M which fuels its active nucleus. The AGN of NGC 7582 is Compton thick and the broad line region is

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obscured optically. With a disk inclined 65 degrees, the galaxy has significant line-of-sight velocities, allowing for the analysis of rotational, radial and other motions of its components. A MUSE datacube containing information on right ascension, declination, and wavelength was collected in 2015 in ESO program 095.A-0934 (PI Juneau). This datacube
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is centered on the optical galactic nucleus and covers 64 sq kpc at the distance of NGC 7582: approximately 22.5 Mpc

(Tully et al. 2013).

2. METHODS
Previous work on this data revealed a flattened kinematically distinct core of fast-moving stars. This ring or disk of stars is approximately 600 pc in diameter, and is centered on the galactic nucleus, which serves to collimate biconical outflows of ionized gas (Prieto et al. 2014, Juneau et al., submitted, hereafter J20). We confirm the presence of this kinematically distinct core and include visualization of the higher-order Gauss-Hermite moments of the stellar kinematics. Furthermore, we present signatures of a large-scale bar in the ionized gas, and we find clear indications of distinct kinematics of the neutral interstellar medium (ISM) traced by the Na D absorption lines; this could be due to differential motion, misaligned rotation, neutral gas outflows or a combination of these. The data used in this analysis were collected through ESO program 095.A-0934 (PI Juneau). With dimensions in right ascension and declination and a third dimension in wavelength, the spectral pixels, or ”spaxels” compose a

  • ˚
  • ˚
  • ˚

3-dimensional dataset. The datacube’s wavelength range is 4750A to 9352A, with a step size of 1.25A, yielding 3682

spectral datapoints per spatial coordinate, and each side of the datacube covers 1’ of sky, or approximately 8kpc at

  • ˚
  • ˚

the distance to NGC 7582. The datacube was spectrally trimmed to span 4750A to 8900A using the muse python data

analysis framework (MPDAF) (Bacon et al. 2016), and this spectrally trimmed datacube was used for analysis. A white light image, created by summing the flux across the entire spectrum in each spaxel using the MPDAF package, is shown in Fig 1. Analysis of the reduced datacube began with the GIST pipeline (Bittner et al. 2019a). The pipeline first creates Voronoi Bins of the datacube (Cappel- lari & Copin 2003), such that the spectra across all bins have constant or nearconstant signal-to-noise ratios, a parameter determined by the GIST user. The pipeline then performs penalized pixel fitting (pPXF) (Cappellari 2017) of the binned spectra to fit the stellar continuum. This fit yields line-of-sight velocity distribution in the galaxy’s rest frame, allowing for the user to analyze the line-of-sight velocity, velocity disperion, skewness of the velocity, and kurtosis of the dispersion. Then, GIST performs an analysis of select emission and absorption lines using the GANDALF module(Sarzi et al. 2017), which treats each emission or absorption line input to the pipeline as

Figure 1. White light image NGC 7582, created by summing the flux over each spaxel f the MUSE datacube using the MPDAF package. Each side

a Gaussian template, and by combin-

measures 8kpc, centered on the optical galactic nucleus. The blue, green, and

ing the given templates with those from

red stars in the Southeast, center and Northwest of the galaxy correspond to the respectively colored spectra in Figs 2 and 6

an input spectral template library, GIST finds and stores the kinematic information – velocity and velocity dispersion –
.and the flux and amplitude of the emission and absorption lines (Sarzi et al. 2006). A full description of the GIST pipeline’s capabilities can be found in the work by Bittner and colleagues, and in the online documentation (Bittner et al. 2019b). We selected a target signal-to-noise ratio of 50 and a minimum signal-to-noise ratio of 3 for the Voronoi binning step of the GIST pipeline. Any bins that could not meet the minimum SNR were excluded from the analysis and not plotted, while individual spaxels that met or exceeded the target SNR were left as individual spaxels and not included

NGC7582 Kinematics

3in larger bins. E-MILES, the Extended MILES stellar population models Vazdekis et al. (2016), served as our input library of spectral templates for the pPXF module of the GIST pipeline. Though E-MILES’s spectral range runs from

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  • ˚

0.168µm to 5.0µm, we selected the range from 4750A to 8900A , because the spectral range of the MUSE datacube is

  • ˚
  • ˚
  • ˚

4750A to 9500A, with poor sky subtraction and no prominent astronomical emission or absorption lines past 8900A.

In addition to the GIST pipeline default emission line fits, we fit for sodium-D absorption lines, blue wings of all emission lines within the spectral range, and red wings of Hα, Hβ, [N ii] λ6584, and [O iii] λλ4959, 5007. Emission lines corresponding to the galactic disk were tied to Hα, as this line is strong where there is star formation and stellar activity, which occurs in the galaxy disk (Baldwin et al. 1981); emission lines in the red and blue wings were tied to [O iii] λ5007, as this line is a strong tracer for gas ionized by an AGN (Peterson 1997). Initial guesses for the velocity of the gas in the blue wings were set to -200 km/s, while intial guesses for the red wings were set to +200 km/s. The wings are expected to account for outflowing gas towards and away from the observer, respectively. Though the GIST pipeline automatically generates kinematic maps, we elected to generate our own maps for the purpose of analysis. This was done by modifying the GIST sourcecode in a Jupyter Notebook, on the Astro Data Lab server (Fitzpatrick et al. 2014), to enable the user to create maps of flux and amplitude line ratios, dispersion-velocity ratios and the difference of gaseous and stellar kinematics. Our modified code also allows the user to customize the colormaps and colorbars of the plots, and to display multiple maps in one figure. These modifications allow for specific analyses not supported by the GIST pipeline’s default output maps and visualization settings.

3. RESULTS
We analyzed the kinematics of the stars, ionized and neutral gas in NGC 7582. To illustrate, we extracted spectra three different regions of the galaxy, shown in Fig 2. These spectra were each created from the ESO-reduced MUSE datacube using MPDAF to sum the flux of 25 pixels in a 5x5 square centered on the location of the marker star symbols seen in Fig 1. The green-colored spectrum seen in Fig 2 corresponds the center of the galaxy indicated by the green star in Fig 1, the blue-colored spectrum corresponds to the Southeast region of the galaxy indicated by the blue star marker, and the red-colored spectrum is from the Northwest region of the galaxy shown by the red star marker. Visual analysis of Fig 2 reveals blue-shifts in the [O iii] λ5007, [O i], and [Ar iii]emission lines in the center of NGC 7582 that are not seen – if the emission lines appear – in the spectra from the Northwest and Southeast regions of the galaxy. However, a more detailed analysis of NGC 7582’s spectra using the GIST pipeline is necessary to develop a greater understanding of NGC 7582’s kinematics. We present results on the stellar kinematics in section 3.1, on the kinematics of ionized gas in section 3.2, and finally, results on the kinematics of neutral gas in the ISM – as traced by Na D – in section 3.3.

Figure 2. Rest frame spectra of NGC 7582 from 3 regions of the galaxy: Center (green), Northwest (red), and Southeast (blue), corresponding to the location of the star symbols in Fig 1. Each spectra is created using MPDAF, and is comprised of the summed spectra of 25 spaxels located in 5x5 spaxels squares in the respective galactic regions. Overplotted in fuchsia are dotted vertical lines marking Hβ, [O i] λ6300, Na D, and Hα, [S ii], and [Ar iii]emission or absorption lines. Note that the flux
˚of the central spectra has been divided by 8. Additional features, such as the [Ca ii] triplet around 8500A.

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3.1. Stellar Kinematics

The stellar kinematics, seen in Fig. 3, show the large-scale counter-clockwise rotation of NGC 7582’s galactic disk and its kinematically distinct core. This core rotates more rapidly than the surrounding stars and shows a drop in velocity dispersion compared to the surrounding stars; in Fig 3’s σ panel (top right), the stars surrounding the core have σ of 120-150 km/s, while the core has a σ of roughly 75 km/s. The rise in velocity dispersion surrounding the core could be due to a number of factors: a co-rotating disk of an inclination offset from the inclination angle of the galaxy, a galactic bulge, and disruption by the galactic bars. In the bottom panels of Fig 3, we see that the higher-order Gauss-Hermite moments have local extrema near the galactic core. The third moment (h3) is a measure

Figure 3. Voronoi-binned stellar kinematics of NGC 7582. Note that (0,0) is the center of the image, corresponding to the galactic center of NGC 7582, and that ∆δ and ∆α are not sky coordinates but coordinates in the galaxy. Top Left: Stellar Velocity (km/s), v. Colormap ranges from -150 km/s (dark blue) to +150 km/s (dark red). Top Right: Stellar velocity dispersion, σ. Colormap ranges from 0 km/s (dark blue) to 150 km/s (dark red). Bottom Left: 3rd order Gauss-Hermite moment, representing the skewness of the velocity Gaussian spread. The colormap ranges from -0.2 (dark red) to +0.2 (dark blue). Red colors indicate skewness to the right of the median, while bluer colors indicate skewness toward the left of the median. Bottom Right: 4th order Gauss-Hermite moment, representing the kurtosis of the velocity dispersion. The colormap ranges from 0.0 (dark blue) to 0.2 (dark red).

NGC7582 Kinematics

5of the velocity distribution’s skewness, which indicates deviations from a normal distribution. In the bottom left panel of Fig 3, we see that the distribution is skewed towards bluer wavelength in the South end of the kinematically distinct core and along the approaching side of the galaxy’s semimajor axis. Conversely, the distribution is skewed towards redder wavelengths in the North end of the kinematically distinct core and in the redshifted side of the galaxy. The high values of skewness in the kinematically distinct core may indicate the necessity for multiple velocity distribution components to fully describe the stellar velocity field. The fourth Gauss-hermite moment (h4), in the bottom left panel of Fig 3, is a measure of the kurtosis of the velocity distribution; that is, the tail-heaviness or peakedness of the distribution. Overall, the stellar velocity distribution is not tail-heavy a and not steeply peaked as all of the values of the third moment are < 1. We do see a local maxima in the central few arcseconds of the kurtosis map, indicating that the distribution there is more tail-heavy and more steeply peaked than elsewhere in the galaxy. The same region shows a drop in velocity dispersion, interestingly, suggesting that there is comparatively more coherent stellar motion in that area than the surrounding area.

3.2. Ionized Gas Kinematics

An intriguing aspect of research is how the gas kinematics relate to the stellar kinematics in galaxies with active nuclei. Fig 4 shows the kinematics of the three components of [N ii] λ6584: the blue wing, the component of the galactic disk, and the red wing, respectively. The top panels show the velocity, v, and the bottom panels show the velocity dispersion, σ. The middle panel of Figs 4 and 5 shows large-scale rotation following the same counter-clockwise direction as the stellar velocity field seen in Fig 3. The signatures of low-high-low velocity accompanied by high-lowhigh dispersion along the major axis are likely along the leading edge of the galactic bar, which may indicate funneling and/or piling up of gas along the bar. The regions of relatively high velocity dispersion of gas near the center of the galaxy – and not along the major axis – likely correspond to the outflowing gas described in J20. The ionized gas outflows distort the middle velocity maps of Figs 4 and 5 at approximately (10”, 0”), and in a diagonal line in the Southwest quadrant of the map. The edges of the outflow cone are again visible in the σ map, appearing as regions of relatively higher σ. Signatures of outflows are seen in the left and right panels of Figs 4 and 5. In the left panels of both figures, we see a highly negative velocity stripe with velocity dispersion of 70-80 km/s running from approximately (0”,0”) to (10”,-30”); the maps show another, less clear, stripe running roughly horizontally from (0”, 0”) to (20”, 0”). This is the blue wing component predominantly corresponding to the edges of the conical outflow of AGN-ionized gas described by J20. The backside of this 3-dimensional, hollow cone is seen at approximately (10”,-5”) and is slightly redshifted relative to the front side of the outflow in both Figs 4 and 5. This spread of velocity could cause a higher σ in the region where both sides of the cone are detected, and might explain the ≥ 150 km/s σ line in the southwest quadrant of the leftmost panel; in the northeast quadrant, the region of higher v and σ most likely corresponds to the cone outflowing from the back side of the galaxy. The bottom (southern) edge of the cone appears to have a parabolic shape, although the top edge of the front cone is not defined well enough to determine if the shape is symmetrical. The rightmost panels of Fig 4 show the red wing of ionized gas. This is gas that is expected to be greatly redshifted relative to the gas in the galactic disk. The lower edge of the back outflow cone is well defined in the southeast quadrant as a roughly horizontal line of bins from (-5”,-5”) to (-25”,-5”), with velocities ranging from approximately 40 km/s to 160 km/s, and velocity dispersions of approximately 150 km/s. The upper edge of the rear outflow cone can also be seen as a group of bins with v > 160 km/s. The region in the southwest quadrant where v ≥200 km/s and σ of approximately 60 km/s likely corresponds to the back side of the front outflow cone. In Fig 5, the velocity and velocity dispersion of [O iii] λ5007is shown. Juneau and colleagues have studied the outflow of ionized gas from NGC 7582, and this figure offers a different look at the same data used in that study. The left bottom panel of Fig 5, showing the velocity dispersion, shows high velocity dispersion along the cone in the blue wing, corresponding to the cone outflowing from the front-side of NGC 7582. The edges of the cone have a lower σ than the region between. At approximately (-10”,15”) in the map, we see a local maximum of σ, where the velocity dispersion is approximately 90 km/s. This maximum, which can be seen in the velocity map as well, likely marks the nearest edge of the cone outflowing from the backside of NGC 7582, which supports the results by J20. The rightmost panels of 5 show the emission line fit for the red wing of [O iii] λ5007. However, because of the red wing’s low signal-to-noise ratio, the kinematic maps of this ionized gas are unfortunately not especially informative. In the velocity plot of the [O iii] λ5007component in the disk of the galaxy, the galactic bar appears as a slight dip in velocity accompanied by a rise in velocity. The three-component fit performed by the GANDALF module does
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Figure 4. Kinematics of three components of [N ii] λ6584 in NGC 7582. Top Row: Velocity of three components of [N ii] are plotted. Colormap ranges from -200 km/s (dark blue) to +200 km/s (dark red). Left: Velocity fit with the blue wing gaussian component. Middle: Velocity of fit with the central core gaussian component. Right: Velocity of fit with the red wing gaussian component. Bottom Row: Velocity dispersion, σ of three components of [N ii]. Colormap ranges from 0 km/s (dark blue) to 150 km/s (dark red). Left: σ of [N ii] fit using the blue wing gaussian component. Middle: σ fit using the central core gaussian component. Right: σ fit using the red wing gaussian component.

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  • The Iso Handbook

    The Iso Handbook

    THE ISO HANDBOOK Volume I: ISO – Mission & Satellite Overview Martin F. Kessler1,2, Thomas G. M¨uller1,4, Kieron Leech 1, Christophe Arviset1, Pedro Garc´ıa-Lario1, Leo Metcalfe1, Andy M. T. Pollock1,3, Timo Prusti1,2 and Alberto Salama1 SAI-2000-035/Dc, Version 2.0 November, 2003 1 ISO Data Centre, Science Operations and Data Systems Division Research and Scientific Support Department of ESA, Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid, Spain 2 ESTEC, Science Operations and Data Systems Division Research and Scientific Support Department of ESA, Keplerlaan 1, Postbus 299, 2200 AG Noordwijk, The Netherlands 3 Computer & Scientific Co. Ltd., 230 Graham Road, Sheffield S10 3GS, England 4 Max-Planck-Institut f¨ur extraterrestrische Physik, Giessenbachstraße, D-85748 Garching, Germany ii Document Information Document: The ISO Handbook Volume: I Title: ISO - Mission & Satellite Overview Reference Number: SAI/2000-035/Dc Issue: Version 2.0 Issue Date: November 2003 Authors: M.F. Kessler, T. M¨uller, K. Leech et al. Editors: T. M¨uller, J. Blommaert & P. Garc´ıa-Lario Web-Editor: J. Matagne Document History The ISO Handbook, Volume I: ISO – Mission & Satellite Overview is mainly based on the following documents: • The ISO Handbook, Volume I: ISO – Mission Overview, Kessler M.F., M¨uller T.G., Arviset C. et al., earlier versions, SAI-2000-035/Dc. • The ISO Handbook, Volume II: ISO – The Satellite and its Data, K. Leech & A.M.T. Pollock, earlier versions, SAI-99-082/Dc. • The following ESA Bulletin articles: The ISO Mission – A Scientific Overview, M.F. Kessler, A.
  • The Nuclear Regions of NGC 7582 from [Ne II] Spectroscopy at 12.8 Μm – an Estimate of the Black Hole Mass

    The Nuclear Regions of NGC 7582 from [Ne II] Spectroscopy at 12.8 Μm – an Estimate of the Black Hole Mass

    A&A 460, 449–457 (2006) Astronomy DOI: 10.1051/0004-6361:20053385 & c ESO 2006 Astrophysics The nuclear regions of NGC 7582 from [Ne II] spectroscopy at 12.8 µm – an estimate of the black hole mass M. Wold1,M.Lacy2,H.U.Käufl1, and R. Siebenmorgen1 1 European Southern Observatory, Karl-Schwarzschild str. 2, 85748 Garching bei München, Germany e-mail: [email protected] 2 Spitzer Science Center, California Institute of Technology, Caltech, MC 220-6, Pasadena, CA 91125, USA Received 9 May 2005 / Accepted 10 August 2006 ABSTRACT We present a high-resolution (R ≈ 16 000) spectrum and a narrow-band image centered on the [Ne ii]12.8 µm line of the central kpc region of the starburst/Seyfert 2 galaxy NGC 7582. The galaxy has a rotating circum-nuclear starburst disk, shown at great detail at a diffraction-limited resolution of 0. 4(≈40 pc). The high spatial resolution allows us to probe the dynamics of the [Ne ii]gasin the nuclear regions, and to estimate the mass of the central black hole. We construct models of gas disks rotating in the combined 7 gravitational potential from the stellar bulge and a central black hole, and derive a black hole mass of 5.5 × 10 M with a 95% 7 confidence interval of [3.6, 8.1] × 10 M. The black hole mass combined with stellar velocity dispersion measurements from the literature shows that the galaxy is consistent with the local MBH-σ∗ relation. This is the first time that a black hole mass in a galaxy except our own Milky Way system has been estimated from gas dynamics in the mid-infrared.
  • Download PDF of Abstracts

    Download PDF of Abstracts

    15th HEAD Naples, FL – April, 2016 Meeting Program Session Table of Contents 100 – AGN I Analysis Poster Session 206 – Early Results from the Astro-H 101 – Galaxy Clusters 116 – Missions & Instruments Poster Mission 102 – Dissertation Prize Talk: Accretion Session 207 – Stellar Compact II driven outflows across the black hole mass 117 – Solar and Stellar Poster Session 300 – The Physics of Accretion Disks – A scale, Ashley King (KIPAC/Stanford 118 – Supernovae and Supernova Joint HEAD/LAD Session University) Remnants Poster Session 301 – Gravitational Waves 103 – Time Domain Astronomy 119 – WDs & CVs Poster Session 302 – Missions & Instruments 104 – Feedback from Accreting Binaries in 120 – XRBs and Population Surveys Poster 303 – Mid-Career Prize Talk: In the Ring Cosmological Scales Session with Circinus X-1: A Three-Round Struggle 105 – Stellar Compact I 200 – Solar Wind Charge Exchange: to Reveal its Secrets, Sebastian Heinz 106 – AGNs Poster Session Measurements and Models (Univ. of Wisconsin) 107 – Astroparticles, Cosmic Rays, and 201 – TeraGauss, Gigatons, and 304 – Science of X-ray Polarimetry in the Neutrinos Poster Session MegaKelvin: Theory and Observations of 21st Century 108 – Cosmic Backgrounds and Deep Accretion Column Physics 305 – Making the Multimessenger – EM Surveys Poster Session 202 – The Structure of the Inner Accretion Connection 109 – Galactic Black Holes Poster Session Flow of Stellar-Mass and Supermassive 306 – SNR/GRB/Gravitational Waves 110 – Galaxies and ISM Poster Session Black Holes 400 – AGN II 111 – Galaxy
  • Radio Emission of the Nuclei of Barred Spiral Galaxies

    Radio Emission of the Nuclei of Barred Spiral Galaxies

    RADIO EMISSION OF THE NUCLEI OF BARRED SPIRAL GALAXIES By H. M. TOVMASSIAN* [Manuscript received May 27, 1966] Summary The results of radio observations of 98 barred galaxies at 11, 21, and 75 cm are presented. The observations were carried out with the 210 ft radio telescope of the Australian National Radio Astronomy Observatory and with the Mills Oross of the Sydney University Molonglo Radio Observatory. Radio emission originating within 1· 5 minutes of arc of the centre of corresponding galaxies was detected in 21 cases. It is concluded that the central parts of galaxies (possibly their nuclei) are responsible for the radio emission. Spectral indices of detected sources were determined. Radio indices show that radio emissivity of the majority of the investi­ gated galaxies is higher than that of normal galaxies. I. INTRODUCTION For some years after the discovery of radio galaxies, collisions between galaxies were accepted by many as the cause of the intense radio emission (Baade and Minkowski 1954; Shklowski 1954; and others). Ambartsumian (1956a) was the first to reject the idea of random collisions as an explanation of the observed phenomena. He came to this conclusion by considering certain observational data, particularly that a collision is an extremely rare event among the superluminous galaxies to which the radio galaxies belong. Subsequently he proposed and developed (Ambartsumian 1956b, 1958, 1962) a theory stressing the importance of the activity of the nuclei in the formation and evolution of galaxies. Some forms of nuclear activ­ ity result in powerful radio emission. Nowadays the hypothesis of nuclear activity is widely accepted and there is much observational evidence in favour of it.
  • Cold Molecular Gas and PAH Emission in the Nuclear and Circumnuclear Regions of Seyfert Galaxies.', Astronomy Astrophysics., 639

    Cold Molecular Gas and PAH Emission in the Nuclear and Circumnuclear Regions of Seyfert Galaxies.', Astronomy Astrophysics., 639

    Durham Research Online Deposited in DRO: 06 August 2020 Version of attached le: Published Version Peer-review status of attached le: Peer-reviewed Citation for published item: Alonso-Herrero, A. and Pereira-Santaella, M. and Rigopoulou, D. and Garc¡a-Bernete,I. and Garc¡a-Burillo, S. and Dom¡nguez-Fern¡andez,A. J. and Combes, F. and Davies, R. I. and D¡az-Santos, T. and Esparza-Arredondo, D. and Gonz¡alez-Mart¡n,O. and Hern¡an-Caballero, A. and Hicks, E. K. S. and H¤onig,S. F. and Levenson, N. A. and Ramos Almeida, C. and Roche, P. F. and Rosario, D. (2020) 'Cold molecular gas and PAH emission in the nuclear and circumnuclear regions of Seyfert galaxies.', Astronomy astrophysics., 639 . A43. Further information on publisher's website: https://doi.org/10.1051/0004-6361/202037642 Publisher's copyright statement: Alonso-Herrero, A., Pereira-Santaella, M., Rigopoulou, D., Garc¡a-Bernete,I., Garc¡a-Burillo,S., Dom¡nguez-Fern¡andez,A. J., Combes, F., Davies, R. I., D¡az-Santos, T., Esparza-Arredondo, D., Gonz¡alez-Mart¡n, O., Hern¡an-Caballero,A., Hicks, E. K. S., H¤onig,S. F., Levenson, N. A., Ramos Almeida, C., Roche, P. F. Rosario, D. (2020). Cold molecular gas and PAH emission in the nuclear and circumnuclear regions of Seyfert galaxies. Astronomy Astrophysics 639: A43, reproduced with permission, c ESO. Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.
  • H-Alpha Imaging of Early-Type (Sa-Sab) Spiral Galaxies I

    H-Alpha Imaging of Early-Type (Sa-Sab) Spiral Galaxies I

    Hα Imaging of Early-Type(Sa-Sab) Spiral Galaxies I1 Salman Hameed2, Nick Devereux2 Astronomy Department, New Mexico State University, Las Cruces, NM 88003 ABSTRACT Hα and continuum images are presented for 27 nearby early-type(Sa-Sab) spiral galaxies. Contrary to popular perception, the images reveal copious massive star formation in some of these galaxies. A determination of the Hα morphology and a measure of the Hα luminosity suggests that early-type spirals can be classified into two broad categories based on the luminosity of largest H II region in the disk. The first category includes galaxies for which the 39 −1 individual H II regions have LHα < 10 ergs . Most of the category 1 galaxies appear to be morphologically undisturbed, but show a wide diversity in nuclear Hα properties. The second category includes galaxies which have at least one 39 −1 H II region in the disk with LHα ≥ 10 ergs . All category 2 galaxies show either prominent dust lanes or other morphological peculiarities such as tidal tails which suggests that the anomalously luminous H II regions in category 2 galaxies may have formed as a result of a recent interaction. The observations, which are part of an on-going Hα survey, reveal early-type spirals to be a heterogeneous class of galaxies that are evolving in the current epoch. We have also identified some systematic differences between the classifications of spiral galaxies in the Second General Catalog (RC2) and the Revised Shapley- Ames Catalog (RSA) which may be traced to subtle variations in the application of the criteria used for classifying spiral galaxies.
  • Astronomy Magazine 2020 Index

    Astronomy Magazine 2020 Index

    Astronomy Magazine 2020 Index SUBJECT A AAVSO (American Association of Variable Star Observers), Spectroscopic Database (AVSpec), 2:15 Abell 21 (Medusa Nebula), 2:56, 59 Abell 85 (galaxy), 4:11 Abell 2384 (galaxy cluster), 9:12 Abell 3574 (galaxy cluster), 6:73 active galactic nuclei (AGNs). See black holes Aerojet Rocketdyne, 9:7 airglow, 6:73 al-Amal spaceprobe, 11:9 Aldebaran (Alpha Tauri) (star), binocular observation of, 1:62 Alnasl (Gamma Sagittarii) (optical double star), 8:68 Alpha Canum Venaticorum (Cor Caroli) (star), 4:66 Alpha Centauri A (star), 7:34–35 Alpha Centauri B (star), 7:34–35 Alpha Centauri (star system), 7:34 Alpha Orionis. See Betelgeuse (Alpha Orionis) Alpha Scorpii (Antares) (star), 7:68, 10:11 Alpha Tauri (Aldebaran) (star), binocular observation of, 1:62 amateur astronomy AAVSO Spectroscopic Database (AVSpec), 2:15 beginner’s guides, 3:66, 12:58 brown dwarfs discovered by citizen scientists, 12:13 discovery and observation of exoplanets, 6:54–57 mindful observation, 11:14 Planetary Society awards, 5:13 satellite tracking, 2:62 women in astronomy clubs, 8:66, 9:64 Amateur Telescope Makers of Boston (ATMoB), 8:66 American Association of Variable Star Observers (AAVSO), Spectroscopic Database (AVSpec), 2:15 Andromeda Galaxy (M31) binocular observations of, 12:60 consumption of dwarf galaxies, 2:11 images of, 3:72, 6:31 satellite galaxies, 11:62 Antares (Alpha Scorpii) (star), 7:68, 10:11 Antennae galaxies (NGC 4038 and NGC 4039), 3:28 Apollo missions commemorative postage stamps, 11:54–55 extravehicular activity