Julia Dusk Kennefick

Discovery of a relationship between spiral arm morphology and supermassive black hole mass in disk galaxies

We present a relationship between spiral arm pitch angle (a measure of the tightness of spiral structure) and the mass of supermassive black holes (BHs) in the nuclei of disk galaxies. We argue that this relationship is expected through a combination of other relationships, whose existence has already been demonstrated. The recent discovery of AGN in bulgeless disk galaxies suggests that halo concentration or virial mass may be one of the determining factors in BH mass. Taken together with the result that mass concentration seems to determine spiral arm pitch angle, one would expect a relation to exist between spiral arm pitch angle and supermassive BH mass in disk galaxies, and we find that this is indeed the case. We conclude that this relationship may be important for estimating evolution in BH masses in disk galaxies out to intermediate redshifts, since regular spiral arm structure can be seen in galaxies out to z 1.

MEASUREMENT OF GALACTIC LOGARITHMIC SPIRAL ARM PITCH ANGLE USING TWO-DIMENSIONAL FAST FOURIER TRANSFORM DECOMPOSITION

A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing two-dimensional fast Fourier transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow comparison of spiral galaxy pitch angle to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques.

Identification of Outflows and Candidate Dual Active Galactic Nuclei in SDSS Quasars at z = 0.8-1.6

We present a sample of 131 quasars from the Sloan Digital Sky Survey at redshifts 0.8 < z < 1.6 with double peaks in either of the high-ionization narrow emission lines [Ne V] λ3426 or [Ne III] λ3869. These sources were selected with the intention of identifying high-redshift analogs of the z < 0.8 active galactic nuclei (AGNs) with double-peaked [O III] λ5007 lines, which might represent AGN outflows or dual AGNs. Lines of high ionization potential are believed to originate in the inner, highly photoionized portion of the narrow line region, and we exploit this assumption to investigate the possible kinematic origins of the double-peaked lines. For comparison, we measure the [Ne V] λ3426 and [Ne III] λ3869 double peaks in low-redshift (z < 0.8) [O III]-selected sources. We find that [Ne V] λ3426 and [Ne III] λ3869 show a correlation between line splitting and line width similar to that of [O III] λ5007 in other studies, and the velocity splittings are correlated with the quasar Eddington ratio. These results suggest an outflow origin for at least a subset of the double peaks, allowing us to study the high-ionization gas kinematics around quasars. However, we find that a non-negligible fraction of our sample show no evidence for an ionization stratification. For these sources, the outflow scenario is less compelling, leaving the dual AGN scenario as a viable possibility. Finally, we find that our sample shows an anti-correlation between the velocity-offset ratio and luminosity ratio of the components, which is a potential dynamical argument for the presence of dual AGNs. Therefore, this study serves as a first attempt at extending the selection of candidate dual AGNs to higher redshifts.

FURTHER EVIDENCE FOR A SUPERMASSIVE BLACK HOLE MASS-PITCH ANGLE RELATION

We present new and stronger evidence for a previously reported relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M {sub BH} of a disk galaxys nuclear supermassive black hole (SMBH). We use an improved method to accurately measure the spiral arm pitch angle in disk galaxies to generate quantitative data on this morphological feature for 34 galaxies with directly measured black hole masses. We find a relation of log (M/M {sub ☉}) = (8.21 ± 0.16) – (0.062 ± 0.009)P. This method is compared with other means of estimating black hole mass to determine its effectiveness and usefulness relative to other existing relations. We argue that such a relationship is predicted by leading theories of spiral structure in disk galaxies, including the density wave theory. We propose this relationship as a tool for estimating SMBH masses in disk galaxies. This tool is potentially superior when compared to other methods for this class of galaxy and has the advantage of being unambiguously measurable from imaging data alone.

On the link between central black holes, bar dynamics and dark matter haloes in spiral galaxies

The discovery of a relationship between supermassive black hole (SMBH) mass and spiral arm pitch angle (P) is evidence that SMBHs are tied to the overall secular evolution of a galaxy. The discovery of SMBHs in late-type galaxies with little or no bulge suggests that an underlying correlation between the dark matter halo concentration and SMBH mass (MBH) exists, rather than between the bulge mass and MBH. In this paper we measure P using a two-dimensional fast fourier transform and estimate the bar pattern speeds of 40 barred spiral galaxies from the Carnegie-Irvine Galaxy Survey. The pattern speeds were derived by estimating the gravitational potentials of our galaxies from Ks-band images and using them to produce dynamical simulation models. The pattern speeds allow us to identify those galaxies with low central dark halo densities, or fast rotating bars, while P provides an estimate of MBH. We find that a wide range of MBH exists in galaxies with low central dark matter halo densities, which appears to support other theoretical results. We also find that galaxies with low central dark halo densities appear to follow more predictable trends in P versus de Vaucouleurs morphological type (T) and bar strength versus T than barred galaxies in general. The empirical relationship between MBH and total gravitational mass of a galaxy (Mtot) allows us to predict the minimum Mtot that will be observationally measured of our fast bar galaxies. These predictions will be investigated in a subsequent paper.

A Deep Multicolor Survey.III.Additional Spectroscopy and Implications for the Number Counts of Faint Quasars

We have made spectroscopic identifications of 39 additional quasar candidates from the Deep Multicolor Survey (DMS) of Hall et al. (1996, ApJ, 462, 614, astro-ph/9512052). We have identified 9 new quasars with 0.3 3 were found among the observed candidates selected due to their red (B-R) and (V-R) colors. As a result, there are now 55 confirmed quasars in the survey: 42 with 0.3 3 over predictions based on models by Warren, Hewett, & Osmer is less than previously suggested. We also demonstrate the success of our quasar color modeling which is important in assessing the completeness of our survey.

A FUNDAMENTAL PLANE OF SPIRAL STRUCTURE IN DISK GALAXIES

Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is correct. Many versions of the density wave theory demand that the pitch angle be uniquely determined by the distribution of mass in the bulge and disk of the galaxy. We present evidence that the tangent of the pitch angle of logarithmic spiral arms in disk galaxies correlates strongly with the density of neutral atomic hydrogen in the disk and with the central stellar bulge mass of the galaxy. These three quantities, when plotted against each other, form a planar relationship that we argue should be fundamental to our understanding of spiral structure in disk galaxies. We further argue that any successful theory of spiral structure must be able to explain this relationship.

Infrared Imaging of Sloan Digital Sky Survey Quasars: Implications for the Quasar K Correction

We have imaged 45 quasars from the Sloan Digital Sky Survey (SDSS) with redshifts 1.85 < z < 4.26 in JHKs with the Kitt Peak National Observatory simultaneous quad infrared imaging device imager. By combining these data with optical magnitudes from the SDSS we have computed the rest-frame optical spectral indices of this sample and investigate their relation with quasar redshift. We find a mean spectral index of α o = –0.55 ± 0.42 with a large spread in values. We also find possible evolution of the form α o = (0.148 ± 0.068)z – (0.964 ± 0.200) in the luminosity range –28.0 < Mi < –26.5. Such evolution suggests changes in the accretion process in quasars with time and is shown to have an effect on computed quasar luminosity functions.

STRONG EVIDENCE FOR THE DENSITY-WAVE THEORY OF SPIRAL STRUCTURE IN DISK GALAXIES

The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxys image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 {\mu}m) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 {\mu}m images have smaller pitch angles than the infrared 8.0 {\mu}m image in all cases, in agreement with the prediction of density-wave theory. We also used images in the ultraviolet from Galaxy Evolution Explorer, whose pitch angles agreed with the measurements made at 8 {\mu}m.

The BTC40 Survey for Quasars at 4.8 < z < 6*

The BTC40 Survey for high-redshift quasars is a multicolor search using images obtained with the Big Throughput Camera (BTC) on the Cerro Tololo Inter-American Observatory (CTIO) 4 m telescope in V, I, and z filters to search for quasars at redshifts of 4.8 < z < 6. The survey covers 40 deg2 in B, V, and I, and 36 deg2 in z. Limiting magnitudes (3 σ) reach to V = 24.6, I = 22.9, and z = 22.9. We used the V-I versus I-z two-color diagram to select high-redshift quasar candidates from the objects classified as point sources in the imaging data. Follow-up spectroscopy with the Anglo-Australian Telescope and CTIO 4 m telescopes of candidates having I ≤ 21.5 has yielded two quasars with redshifts of z = 4.6 and z = 4.8, as well as four emission-line galaxies with z ≈ 0.6. Fainter candidates have been identified down to I = 22 for future spectroscopy on 8 m class telescopes.