arXiv subjects

D. Batcheldor

Publications and source records attributed to D. Batcheldor.

At least 19 recordsLinked to original sources

arXiv2019

Quantifying the AGN-driven outflows in ULIRGs (QUADROS) IV: HST/STIS spectroscopy of the sub-kpc warm outflow in F14394+5332

Considerable uncertainties remain about the nature of warm, AGN-driven outflows and their impact on the evolution of galaxies. This is because the outflows are often unresolved in ground-based observations. As part of a project to study the AGN outflows in some of the most rapidly evolving galaxies in the local Universe, here we present HST/STIS observations of F14394+5332E that resolve the sub-kpc warm outflow for the first time in a ULIRG. The observations reveal a compact, high-ionization outflow region (r_max~0.9 kpc) set in a more extensive (r_max~1.4 kpc) halo that is kinematically quiescent and has a lower ionization state. A large line width (600 < FWHM < 1500 km/s) is measured throughout the outflow region, and the outflowing gas shows a steep velocity gradient with radius, with the magnitude of the blueshifted velocities increasing from ~500 to 1800 km/s from the inner to the outer part of the outflow. We interpret the observations in terms of the local acceleration, and hydrodynamic destruction, of dense clouds as they are swept up in a hot, low density wind driven by the AGN. We discuss the implications for measuring the mass outflow rates and kinetic powers for the AGN-driven outflows in such objects.

astro-ph.GA↗

arXiv2018

Quantifying the AGN-driven outflows in ULIRGs (QUADROS) II: evidence for compact outflow regions from HST [OIII] imaging observations

The true importance of the warm, AGN-driven outflows for the evolution of galaxies remains uncertain. Measurements of the radial extents of the outflows are key for quantifying their masses and kinetic powers, and also establishing whether the AGN outflows are galaxy-wide. Therefore, as part of a larger project to investigate the significance of warm, AGN-driven outflows in the most rapidly evolving galaxies in the local universe, here we present deep Hubble Space Telescope ( HST) narrow-band [OIII]$λ$5007 observations of a complete sample of 8 nearby ULIRGs with optical AGN nuclei. Combined with the complementary information provided by our ground-based spectroscopy, the HST images show that the warm gas outflows are relatively compact for most of the objects in the sample: in three objects the outflow regions are barely resolved at the resolution of HST ($0.065 < R_{[OIII]} < 0.12$ kpc); in a further four cases the outflows are spatially resolved but with flux weighted mean radii in the range $0.65 < R_{[OIII]} < 1.2$ kpc; and in only one object (Mrk273) is there clear evidence for a more extended outflow, with a maximum extent of $R_{[OIII]}\sim5$ kpc. Overall, our observations show little evidence for the galaxy-wide outflows predicted by some models of AGN feedback.

astro-ph.GA↗

arXiv2016

A normal supermassive black hole in NGC 1277

The identification of galaxies with `overly massive' black holes requires two measurements: a black hole mass (M_bh) and a host spheroid mass (M_sph,*). Here we provide our measurements for NGC 1277. Our structural decomposition reveals that NGC 1277 is dominated by a `classical' spheroid with a Sersic index n=5.3, a half-light radius R_e=2.1 kpc, and a stellar mass of 2.7x10^{11} M_sun (using M_*/L_V=11.65, Martin-Navarro et al.). This mass is an order of magnitude greater than originally reported. Using the latest (M_bh)-n, (M_bh)-(M_sph,*) and (M_bh)-sigma relations, the expected black hole mass is respectively (0.57^{+1.29}_{-0.40})x10^9 M_sun, (1.58^{+4.04}_{-1.13})x10^9 M_sun, and (2.27^{+4.04}_{-1.44})x10^9 M_sun (using sigma=300 km/s) for which the `sphere-of-influence' is 0".31. Our new kinematical maps obtained from laser guide star assisted, adaptive optics on the Keck I Telescope dramatically reaffirm the presence of the inner, nearly edge-on, disk seen in this galaxy's image. We also report that this produces a large velocity shear (~400 km/s) across the inner 0".2 (70 pc) plus elevated values of sqrt{sigma^2+(V_rot)^2} across the inner 3".8x0".6 region of the galaxy. Our new multi-Gaussian expansion (MGE) models and Jeans Anisotropic MGE (JAM) analysis struggled to match this extended component. Our optimal black hole mass, albeit a probable upper limit because of the disk, is 1.2x10^9 M_sun (M/L_V=12.3). This is an order of magnitude smaller than originally reported and 4 times smaller than recently reported. It gives an M_bh/M_sph,* ratio of 0.45% in agreement with the median (~0.5%) and range (0.1 to 5.0%) observed in non-dwarf, early-type galaxies. This result highlights the need for caution with inner disks.

astro-ph.GA↗

arXiv2015

Extreme Contrast Ratio Imaging of Sirius with a Charge Injection Device

The next fundamental steps forward in understanding our place in the universe could be a result of advances in extreme contrast ratio (ECR) imaging and point spread function (PSF) suppression. For example, blinded by quasar light we have yet to fully understand the processes of galaxy formation and evolution, and there is an ongoing race to obtain a direct image of an exoearth lost in the glare of its host star. To fully explore the features of these systems we must perform observations in which contrast ratios of at least one billion can be regularly achieved with sub 0.1" inner working angles. Here we present the details of a latest generation 32-bit charge injection device (CID) that could conceivably achieve contrast ratios on the order of one billion. We also demonstrate some of its ECR imaging abilities for astronomical imaging. At a separation of two arc minutes, we report a direct contrast ratio of Delta(m_v)=18.3, log(CR)=7.3, or 1 part in 20 million, from observations of the Sirius field. The atmospheric conditions present during the collection of this data prevented less modest results, and we expect to be able to achieve higher contrast ratios, with improved inner working angles, simply by operating a CID at a world-class observing site. However, CIDs do not directly provide any PSF suppression. Therefore, combining CID imaging with a simple PSF suppression technique like angular differential imaging, could provide a cheap and easy alternative to the complex ECR techniques currently being employed.

astro-ph.IM↗

arXiv2014

Recoiling Supermassive Black Holes: a search in the Nearby Universe

The coalescence of a binary black hole can be accompanied by a large gravitational recoil due to anisotropic emission of gravitational waves. A recoiling supermassive black hole (SBH) can subsequently undergo long-lived oscillations in the potential well of its host galaxy, suggesting that offset SBHs may be common in the cores of massive ellipticals. We have analyzed HST archival images of 14 nearby core ellipticals, finding evidence for small ($\lesssim 10$ pc) displacements between the AGN (locating the SBH) and the center of the galaxy (the mean photocenter) in 10 of them. Excluding objects that may be affected by large-scale isophotal asymmetries, we consider six galaxies to have detected displacements, including M87, where a displacement was previously reported by Batcheldor et al. 2010. In individual objects, these displacements can be attributed to residual gravitational recoil oscillations following a major or minor merger within the last few Gyr. For plausible merger rates, however, there is a high probability of larger displacements than those observed, if SBH coalescence took place in these galaxies. Remarkably, the AGN-photocenter displacements are approximately aligned with the radio source axis in four of the six galaxies with displacements, including three of the four having relatively powerful kpc-scale jets. This suggests intrinsic asymmetries in radio jet power as a possible displacement mechanism, although approximate alignments are also expected for gravitational recoil. Orbital motion in SBH binaries and interactions with massive perturbers can produce the observed displacement amplitudes but do not offer a ready explanation for the alignments.

astro-ph.GA↗

arXiv2014

Near-infrared Hubble Space Telescope polarimetry of a complete sample of narrow-line radio galaxies

We present an analysis of 2.05 $μ$m Hubble Space Telescope (HST) polarimetric data for a sample of 13 nearby Fanaroff-Riley type II (FRII) 3CR radio sources ($0.03<z<0.11$) that are classified as narrow line radio galaxies (NLRG) at optical wavelengths. We find that the compact cores of the NLRG in our sample are intrinsically highly polarised in the near-IR ($6 < P_{2.05μm} < 60$ per cent), with the electric-vector (E-vector) perpendicular to the radio axis in 54 per cent of the sources. The levels of extinction required to produce near-infrared polarisation by the dichroic extinction mechanism are consistent with the measured values reported in Ramírez et al. (2014), provided that this mechanism has its maximum efficiency. This consistency suggests that the nuclear polarisation could be due to dichroic extinction. In this case, toroidal magnetic fields that are highly coherent would be required in the circumnuclear tori to align the elongated dust grains responsible for the dichroic extinction. However, it is not entirely possible to rule out other polarisation mechanisms (e.g. scattering, synchrotron emission) with our observations at only one near-IR wavelength. Therefore further polarimetry observations at mid-IR and radio wavelengths will be required to test whether all the near-IR polarisation is due to dichroic extinction.

astro-ph.GA↗

arXiv2013

A STIS Atlas of CaII Triplet Absorption Line Kinematics in Galactic Nuclei

The relations observed between supermassive black holes and their host galaxies suggest a fundamental link in the processes that cause these two objects to evolve. A more comprehensive understanding of these relations could be gained by increasing the number of supermassive black hole mass (M) measurements. This can be achieved, in part, by continuing to model the stellar dynamics at the centers of galactic bulges using data of the highest possible spatial resolution. Consequently, we present here an atlas of galaxies in the Space Telescope Imaging Spectrograph (STIS) data archive that may have spectra suitable for new M estimates. Archived STIS G750M data for all non-barred galactic bulges are co-aligned and combined, where appropriate, and the radial signal-to-noise ratios calculated. The line-of-sight velocity distributions from the CaII triplet are then determined using a maximum penalized likelihood method. We find 19 out of 42 galaxies may provide useful new M estimates since they are found to have data that is comparable in quality with data that has been used in the past to estimate M. However, we find no relation between the signal-to-noise ratio in the previously analyzed spectra and the uncertainties of the black hole masses derived from the spectra. We also find that there is a very limited number of appropriately observed stellar templates in the archive from which to estimate the effects of template mismatching.

astro-ph.GA↗

arXiv2011

Nicmos Polarimetry of "Polar Scattered" Seyfert 1 Galaxies

The nuclei of Seyfert 1 galaxies exhibit a range of optical polarization characteristics that can be understood in terms of two scattering regions producing orthogonal polarizations: an extended polar scattering region (PSR) and a compact equatorial scattering region (ESR), located within the circum-nuclear torus. Here we present NICMOS 2.0 micron imaging polarimetry of 6 "polar scattered" Seyfert 1 (S1) galaxies, in which the PSR dominates the optical polarization. The unresolved nucleus (<0.58 arcsec) is significantly polarized in only three objects, but 5 of the 6 exhibit polarization in a 0.58 to 1.5 arcsec circum-nuclear annulus. In Fairall 51 and ESO 323-G077, the polarization position angle at 2 microns (theta2m) is consistent with the average for the optical spectrum (thetav), implying that the nuclear polarization is dominated by polar scattering at both wavelengths. The same is probably true for NGC 3227. In both NGC 4593 and Mrk 766, there is a large difference between theta2m and thetav off nucleus, where polar scattering is expected to dominate. This may be due to contamination by interstellar polarization in NGC 4593, but there is no clear explanation in the case of the strongly polarized Mrk 766. Lastly, in Mrk 1239, a large change (~ 60deg) in theta2m between the nucleus and the annulus indicates that the unresolved nucleus and its immediate surroundings have different polarization states at 2 microns, which we attribute to the ESR and PSR, respectively. A further implication is that the source of the scattered 2 micron emission in the unresolved nucleus is the accretion disk, rather than torus hot dust emission.

astro-ph.CO↗

arXiv2010

A Displaced Supermassive Black Hole in M87

Isophotal analysis of M87, using data from the Advanced Camera for Surveys, reveals a projected displacement of 6.8 +/- 0.8 pc (~ 0.1 arcsec) between the nuclear point source (presumed to be the location of the supermassive black hole, SMBH) and the photo-center of the galaxy. The displacement is along a position angle of 307 +/- 17 degrees and is consistent with the jet axis. This suggests the active SMBH in M87 does not currently reside at the galaxy center of mass, but is displaced in the counter-jet direction. Possible explanations for the displacement include orbital motion of an SMBH binary, gravitational perturbations due to massive objects (e.g., globular clusters), acceleration by an asymmetric or intrinsically one-sided jet, and gravitational recoil resulting from the coalescence of an SMBH binary. The displacement direction favors the latter two mechanisms. However, jet asymmetry is only viable, at the observed accretion rate, for a jet age of >0.1 Gyr and if the galaxy restoring force is negligible. This could be the case in the low density core of M87. A moderate recoil ~1 Myr ago might explain the disturbed nature of the nuclear gas disk, could be aligned with the jet axis, and can produce the observed offset. Alternatively, the displacement could be due to residual oscillations resulting from a large recoil that occurred in the aftermath of a major merger any time in the last 1 Gyr.

astro-ph.CO↗

arXiv2010

The M-Sigma Relation Derived from Sphere of Influence Arguments

The observed relation between supermassive black hole (SMBH) mass (M) and bulge stellar velocity dispersion (Sigma) is described by log(M) = alpha + beta*log(Sigma/200 km/s). As this relation has important implications for models of galaxy and SMBH formation and evolution, there continues to be great interest in adding to the M catalog. The "sphere of influence" (r) argument uses spatial resolution to exclude some M estimates and pre-select additional galaxies for further SMBH studies. This Letter quantifies the effects of applying the r argument to a population of galaxies and SMBHs that do not follow the M-Sigma relation. All galaxies with known values of Sigma, closer than 100 Mpc, are given a random M and selected when r is spatially resolved. These random SMBHs produce an M-Sigma relation of alpha=8.3, beta=4.0, consistent with observed values. Consequently, future proposed M estimates should not be justified solely on the basis of resolving r. This Letter shows the observed M-Sigma relation may simply be a result of available spatial resolution. However, it also implies the observed M-Sigma relation defines an upper limit. This potentially provides valuable new insight into the processes of galaxy and SMBH formation and evolution.

astro-ph.CO↗

arXiv2009

The Future of Direct Supermassive Black Hole Mass Estimates

(Abridged) The repeated discovery of supermassive black holes (SMBHs) at the centers of galactic bulges, and the discovery of relations between the SMBH mass (M) and the properties of these bulges, has been fundamental in directing our understanding of both galaxy and SMBH formation and evolution. However, there are still many questions surrounding the SMBH - galaxy relations. For example, are the scaling relations linear and constant throughout cosmic history, and do all SMBHs lie on the scaling relations? These questions can only be answered by further high quality direct M estimates from a wide range in redshift. In this paper we determine the observational requirements necessary to directly determine SMBH masses, across cosmological distances, using current M modeling techniques. We also discuss the SMBH detection abilities of future facilities. We find that if different M modeling techniques, using different spectral features, can be shown to be consistent, then both 30 m ground- and 16 m space-based telescopes will be able to sample M 1e9Msol across ~95% of cosmic history. However, we find that the abilities of ground-based telescopes critically depend on future advancements in adaptive optics systems; more limited AO systems will result in limited effective spatial resolutions, and forces observations towards the near-infrared where spectral features are weaker and more susceptible to sky features. Ground-based AO systems will always be constrained by relatively bright sky backgrounds and atmospheric transmission. The latter forces the use of multiple spectral features and dramatically impacts the SMBH detection efficiency. The most efficient way to advance our database of direct SMBH masses is therefore through the use of a large (16 m) space-based UVOIR telescope.

astro-ph.CO↗

arXiv2009

The Nature of the Near-IR Core Source in 3C 433

We report the analysis of near-infrared imaging, polarimetric and spectroscopic observations of the powerful radio galaxy 3C433, obtained with the HST and UKIRT telescopes. The high spatial resolution of HST allows us to study the near-nuclear regions of the galaxy (<1 kpc). In line with previous observations, we find that 3C433 has an unresolved core source that is detected in all near-IR bands, but dominates over the host galaxy emission at 2.05 um. Our analysis reveals: (1) the presence of a dust lane aligned close to perpendicular (PA$=70\pm5\degr$) to the inner radio jet axis (PA$=-12\pm2\degr$); (2) a steep slope to the near-IR SED ($α=5.8\pm0.1$; F$_ν\proptoν^{-α}$); (3) an apparent lack of broad permitted emission lines at near-IR wavelengths, in particular the absence of a broad Pa$α$ emission line; and (4) high intrinsic polarization for the unresolved core nuclear source ($8.6\pm1$ per cent), with an E-vector perpendicular (PA=$83.0\pm 2.3\degr$) to the inner radio jet. Using five independent techniques we determine an extinction to the compact core source in the range 3 10^4 km/s (FWHM) to escape detection in our near-IR spectrum. Dichroic extinction is the most likely polarization mechanism because it is consistent with the various available extinction estimates. In this case, a highly ordered, coherent toroidal magnetic field must be present in the obscuring structure close to the nucleus.

astro-ph.CO↗

arXiv2008

High Accuracy Near-infrared Imaging Polarimetry with NICMOS

The findings of a nine orbit calibration plan carried out during HST Cycle 15, to fully determine the NICMOS camera 2 (2.0 micron) polarization calibration to high accuracy, are reported. Recently Ueta et al. and Batcheldor et al. have suggested that NICMOS possesses a residual instrumental polarization at a level of 1.2-1.5%. This would completely inhibit the data reduction in a number of GO programs, and hamper the ability of the instrument to perform high accuracy polarimetry. We obtained polarimetric calibration observations of three polarimetric standards at three spacecraft roll angles separated by ~60deg. Combined with archival data, these observations were used to characterize the residual instrumental polarization in order for NICMOS to reach its full potential of accurate imaging polarimetry at p~1%. Using these data, we place an 0.6% upper limit on the instrumental polarization and calculate values of the parallel transmission coefficients that reproduce the ground-based results for the polarimetric standards. The uncertainties associated with the parallel transmission coefficients, a result of the photometric repeatability of the observations, are seen to dominate the accuracy of p and theta. However, the updated coefficients do allow imaging polarimetry of targets with p~1.0% at an accuracy of +/-0.6% and +/-15deg. This work enables a new caliber of science with HST.

astro-ph↗

arXiv2008

High Accuracy Imaging Polarimetry with NICMOS

The ability of NICMOS to perform high accuracy polarimetry is currently hampered by an uncalibrated residual instrumental polarization at a level of 1.2-1.5%. To better quantify and characterize this residual we obtained observations of three polarimetric standard stars at three separate space-craft roll angles. Combined with archival data, these observations were used to characterize the residual instrumental polarization to enable NICMOS to reach its full polarimetric potential. Using these data, we calculate values of the parallel transmission coefficients that reproduce the ground-based results for the polarimetric standards. The uncertainties associated with the parallel transmission coefficients, a result of the photometric repeatability of the observations, dominate the accuracy of p and theta. However, the new coefficients now enable imaging polarimetry of targets with p~1.0% at an accuracy of +/-0.6% and +/-15 degrees.

astro-ph↗

arXiv2008

The M-Sigma Project

There is an intimate link between supermassive black hole (SMBH) mass (M) and the stellar velocity dispersion (sigma) of the host bulge. This has a fundamental impact on our understanding of galaxy and SMBH formation and evolution. However, the scatter, slope and zero-point of the relation is a subject of some debate. For any progress to be made on this relation, the established values of M and sigma must be robust. Over 50% of current M estimates have been made using the technique of stellar dynamics. However, there is serious concern over this method that prompts their re-evaluation. In addition, it is not clear how best to define sigma. The aim of the M-Sigma Project is to use STIS long-slit spectroscopy, integral field spectroscopy and the latest stellar models, to best estimate the values of M and sigma in as many cases as possible. The project will determine the most appropriate properties of the M-Sigma relation itself.

astro-ph↗

arXiv2006

The NICMOS Polarimetric Calibration

The value of accurately knowing the absolute calibration of the polarizing elements in the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) becomes especially important when conducting studies which require measuring degrees of polarization of close to 1% in the near infrared. We present a comprehensive study of all previously observed polarimetric standards using the NIC2 camera on NICMOS. Considering both pre- and post-NICMOS Cooling System observations we find variations in the polarimetry consistent with the effects of sub-pixel mis-alignments and the point spread function. We also measure non-zero results from unpolarized standards indicating an instrumental polarization of p ~ 1.2%, theta ~ 88degrees. The lack of polarized and unpolarized standard stars with which to perform a comprehensive calibration study means we cannot be confident that the current calibration will be effective for a number of recent large NICMOS GO programs. Further observations of polarimetric standards are needed in order to fully characterize the behavior of NICMOS at around p=1%.

astro-ph↗

arXiv2005

Integral Field Spectroscopy of 23 Spiral Bulges

We have obtained Integral Field Spectroscopy for 23 spiral bulges using INTEGRAL on the William Herschel Telescope and SPIRAL on the Anglo-Australian Telescope. This is the first 2D survey directed solely at the bulges of spiral galaxies. Eleven galaxies of the sample do not have previous measurements of the stellar velocity dispersion (sigma*). These data are designed to complement our Space Telescope Imaging Spectrograph program for estimating black hole masses in the range 10^6-10^8M_sun using gas kinematics from nucleated disks. These observations will serve to derive the stellar dynamical bulge properties using the traditional Mgb and CaII triplets. We use both Cross Correlation and Maximum Penalized Likelihood to determine projected sigma* in these systems and present radial velocity fields, major axis rotation curves, curves of growth and sigma* fields. Using the Cross Correlation to extract the low order 2D stellar dynamics we generally see coherent radial rotation and irregular velocity dispersion fields suggesting that sigma* is a non-trivial parameter to estimate.

astro-ph↗

arXiv2005

Nuclear Properties of Nearby Spiral Galaxies from Hubble Space Telescope NICMOS imaging and STIS Spectroscopy

We investigate the central regions of 23 spiral galaxies using archival NICMOS imaging and STIS spectroscopy. The sample is taken from our program to determine the masses of central massive black holes (MBH) in 54 nearby spiral galaxies. Stars are likely to contribute significantly to any dynamical central mass concentration that we find in our MBH program and this paper is part of a series to investigate the nuclear properties of these galaxies. We use the Nuker law to fit surface brightness profiles, derived from the NICMOS images, to look for nuclear star clusters and find possible extended sources in 3 of the 23 galaxies studied (13 per cent). The fact that this fraction is lower than that inferred from optical Hubble Space Telescope studies is probably due to the greater spatial resolution of those studies. Using R-H and J-H colors and equivalent widths of H-alpha emission (from the STIS spectra) we investigate the nature of the stellar population with evolutionary models. Under the assumption of hot stars ionizing the gas, as opposed to a weak AGN, we find that there are young stellar populations (~10-20 Myr) however these data do not allow us to determine what percentage of the total nuclear stellar population they form. Also, in an attempt to find any unknown AGN we use [N II] and [S II] line flux ratios (relative to H-alpha) and find tentative evidence for weak AGN in NGC 1300 and NGC 4536.

astro-ph↗