arXiv subjects

Jacob Noel-Storr

Publications and source records attributed to Jacob Noel-Storr.

12 recordsLinked to original sources

arXiv2022

Q&A: Accessibility in Astronomy for the Visually Impaired

We spoke with four researchers to understand the accessibility challenges in astronomy research, education and outreach for blind and visually impaired (BVI) persons, as well as solutions to these challenges and how it innovates data analysis methods for all astronomers. Those interviewed: Nicolas Bonne (University of Portsmouth); Cheryl Fogle-Hatch (Museum Senses); Garry Foran (Swinburne University of Technology) and Enrique Perez Montero (Instituto de Astrofísica de Andalucía).

astro-ph.IM↗

arXiv2019

Astro2020 APC White Paper: Accessible Astronomy: Policies, Practices, and Strategies to Increase Participation of Astronomers with Disabilities

(Abridged) In this white paper, we outline the major barriers to access within the educational and professional practice of astronomy. We present current best practices for inclusivity and accessibility, including classroom practices, institutional culture, support for infrastructure creation, hiring processes, and outreach initiatives. We present specific ways--beyond simple compliance with the ADA--that funding agencies, astronomers, and institutions can work together to make astronomy as a field more accessible, inclusive, and equitable. In particular, funding agencies should include the accessibility of institutions during proposal evaluation, hold institutions accountable for inaccessibility, and support efforts to gather data on the status and progress of astronomers and astronomy students with disabilities.

astro-ph.IM↗

arXiv2010

HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution

Quillen et al. and O'Dea et al. carried out a Spitzer study of a sample of 62 brightest cluster galaxies (BCGs) from the ROSAT Brightest Cluster Sample chosen based on their elevated H-alpha flux. We present Hubble Space Telescope Advanced Camera for Surveys (ACS) far ultraviolet (FUV) images of the Ly-alpha and continuum emission of the luminous emission-line nebulae in 7 BCGs found to have an infrared excess. We confirm that the BCGs are actively forming stars suggesting that the IR excess seen in these BCGs is indeed associated with star formation. The FUV continuum emission extends over a region of ~7-28 kpc (largest linear size) and even larger in Ly-alpha. The young stellar population required by the FUV observations would produce a significant fraction of the ionizing photons required to power the emission line nebulae. Star formation rates estimated from the FUV continuum range from ~3 to ~14 times lower than those estimated from the IR, however both the Balmer decrement in the central few arcseconds and detection of CO in most of these galaxies imply that there are regions of high extinction that could have absorbed much of the FUV continuum. Analysis of archival VLA observations reveals compact radio sources in all 7 BCGs and kpc scale jets in Abell 1835 and RXJ 2129+00. The four galaxies with archival deep Chandra observations exhibit asymmetric X-ray emission, the peaks of which are offset from the center of the BCGs by ~10 kpc on average. A low feedback state for the AGN could allow increased condensation of the hot gas into the center of the galaxy and the feeding of star formation.

astro-ph.CO↗

arXiv2009

Infrared Diagnostics for the Extended 12 micron Sample of Seyferts

We present an analysis of Spitzer IRS spectroscopy of 83 active galaxies from the extended 12 micron sample. We find rank correlations between several tracers of star formation which suggest that (1) the PAH feature is a reliable tracer of star formation, (2) there is a significant contribution to the heating of the cool dust by stars, (3) the H$_2$ emission is also primarily excited by star formation. The 55-90 vs. 20-30 spectral index plot is also a diagnostic of the relative contribution of Starburst to AGN. We see there is a large change in spectral index across the sample. Thus, the contribution to the IR spectrum from the AGN and starburst components can be comparable in magnitude but the relative contribution also varies widely across the sample. We find rank correlations between several AGN tracers. We search for correlations between AGN and Starburst tracers and we conclude that the AGN and Starburst tracers are not correlated. This is consistent with our conclusion that the relative strength of the AGN and Starburst components varies widely across the sample. Thus, there is no simple link between AGN fueling and Black Hole Growth and star formation in these galaxies. The distribution of Sil 10 micron and 18 micron strengths is consistent with the clumpy torus models of Sirocky et al. We find a rank correlation between the [NeV] 14 micron line and the 6.7 micron continuum which may be due to an extended component of hot dust. The Sy 2s with a Hidden Broad Line Region (HBLR) have a higher ratio of AGN to Starburst contribution to the SED than Sy 2s without an HBLR. This may contribute to the detection of the HBLR in polarized light. The Sy 2s with an HBLR are more similar to the Sy 1s than they are to the Sy 2s without an HBLR.

astro-ph.GA↗

arXiv2009

HST/ACS Emission Line Imaging of Low Redshift 3CR Radio Galaxies I: The Data

We present 19 nearby (z<0.3) 3CR radio galaxies imaged at low- and high-excitation as part of a Cycle 15 Hubble Space Telescope snapshot survey with the Advanced Camera for Surveys. These images consist of exposures of the H-alpha (6563 Å, plus [NII] contamination) and [OIII] 5007 Åemission lines using narrow-band linear ramp filters adjusted according to the redshift of the target. To facilitate continuum subtraction, a single-pointing 60 s line-free exposure was taken with a medium-band filter appropriate for the target's redshift. We discuss the steps taken to reduce these images independently of the automated recalibration pipeline so as to use more recent ACS flat-field data as well as to better reject cosmic rays. We describe the method used to produce continuum-free (pure line-emission) images, and present these images along with qualitative descriptions of the narrow-line region morphologies we observe. We present H-alpha+[NII] and [OIII] line fluxes from aperture photometry, finding the values to fall expectedly on the redshift-luminosity trend from a past HST/WFPC2 emission line study of a larger, generally higher redshift subset of the 3CR. We also find expected trends between emission line luminosity and total radio power, as well as a positive correlation between the size of the emission line region and redshift. We discuss the associated interpretation of these results, and conclude with a summary of future work enabled by this dataset.

astro-ph.CO↗

arXiv2008

An Infrared Survey of Brightest Cluster Galaxies. II: Why are Some Brightest Cluster Galaxies Forming Stars?

Quillen et al.(2007) presented an imaging survey with the {\it Spitzer Space Telescope} of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray luminous clusters. They found that at least half of these sources have signs of excess infrared emission. Here we discuss the nature of the IR emission and its implications for cool core clusters. The strength of the mid-IR excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely related to star formation. The mass of molecular gas (estimated from CO observations) is correlated with the IR luminosity as found for normal star forming galaxies. The gas depletion time scale is about 1 Gyr. The physical extent of the infrared excess is consistent with that of the optical emission line nebulae. This supports the hypothesis that the star formation occurs in molecular gas associated with the emission line nebulae and with evidence that the emission line nebulae are mainly powered by ongoing star formation. We find a correlation between mass deposition rates (${\dot M}_X$) estimated from the X-ray emission and the star formation rate estimated from the infrared luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates suggesting that the re-heating of the ICM is generally very effective in reducing the amount of mass cooling from the hot phase but not eliminating it completely.

astro-ph↗

arXiv2007

An infrared survey of brightest cluster galaxies: Paper I

We report on an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission. These galaxies are located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky Survey. We find that about half of these sources have a sign of excess infrared emission; 22 objects out of 62 are detected at 70 microns, 18 have 8 to 5.8 micron flux ratios above 1.0 and 28 have 24 to 8 micron flux ratios above 1.0. Altogether 35 of 62 objects in our survey exhibit at least one of these signs of infrared excess. Four galaxies with infrared excesses have a 4.5/3.6 micron flux ratio indicating the presence of hot dust, and/or an unresolved nucleus at 8 microns. Three of these have high measured [OIII](5007A)/Hbeta flux ratios suggesting that these four, Abell 1068, Abell 2146, and Zwicky 2089, and R0821+07, host dusty active galactic nuclei (AGNs). 9 objects (including the four hosting dusty AGNs) have infrared luminosities greater than 10^11 L_sol and so can be classified as luminous infrared galaxies (LIRGs). Excluding the four systems hosting dusty AGNs, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely related to star formation.

astro-ph↗

arXiv2006

The Warped Nuclear Disk of Radio Galaxy 3C 449

Among radio galaxies containing nuclear dust disks, the bipolar jet axis is generally observed to be perpendicular to the disk major axis. The FR I radio source 3C 449 is an outlier to this statistical majority, as it possesses a nearly parallel jet/disk orientation on the sky. We examine the 600 pc dusty disk in this galaxy with images from the Hubble Space Telescope. We find that a colormap of the disk exhibits a twist in its isocolor contours (isochromes). We model the colormap by integrating galactic starlight through an absorptive disk, and find that the anomalous twist in the isochromes can be reproduced in the model with a vertically thin, warped disk. The model predicts that the disk is nearly perpendicular to the jet axis within 100 pc of the nucleus. We discuss physical mechanisms capable of causing such a warp. We show that precessional models or a torque on the disk arising from a possible binary black hole in the AGN causes precession on a timescale that is too long to account for the predicted disk morphology. However, we estimate that the pressure in the X-ray emitting interstellar medium is large enough to perturb the disk, and argue that jet-driven anisotropy in the excited ISM may be the cause of the warp. In this way, the warped disk in 3C 449 may be a new manifestation of feedback from an active galactic nucleus.

astro-ph↗

arXiv2006

Understanding the Nuclear Gas Dispersion in Early-Type Galaxies in the Context of Black Hole Demographics

(abridged) We analyze and model HST /STIS observations of a sample of 27 galaxies; 16 Fanaroff & Riley Type I radio galaxies and 11 (more) normal early-type galaxies. We focus here on what can be learned from the nuclear velocity dispersion (line width) of the gas as a complement to the many studies dealing with gas rotation velocities. We find that the dispersion in a STIS aperture of ~0.1''-0.2'' generally exceeds the large-scale stellar velocity dispersion of the galaxy. This is qualitatively consistent with the presence of central BHs, but raises the question whether the excess gas dispersion is of gravitational or non-gravitational origin and whether the implied BH masses are consistent with our current understanding of BH demography(as predicted by the M-sigma relation between BH mass and stellar velocity dispersion). To address this we construct dynamical models for the gas, both thin disk models and models with more general axis ratios and velocity anisotropies. For the normal galaxies the nuclear gas dispersions are adequately reproduced assuming disks around BHs with masses that follow the M-sigma relation. In contrast, the gas dispersions observed for the radio galaxies generally exceed those predicted by any of the models. We attribute this to the presence of non-gravitational motions in the gas that are similar to or larger than the gravitational motions. The non- gravitational motions are presumably driven by the active galactic nucleus (AGN), but we do not find a relation between the radiative output of the AGN and the non-gravitational dispersion. It is not possible to uniquely determine the BH mass for each galaxy from its nuclear gas dispersion. However, for the sample as a whole the observed dispersions do not provide evidence for significant deviations from the M-sigma relation.

astro-ph↗

arXiv2004

The role of immersive informal science programs

Immersive informal environments (such as summer camps, residential programs at museums and science centers, etc.) can provide a venue for young people to explore their scientific thinking in a less formalized context than is available in most traditional classrooms. While class instruction is beneficial for children to develop formal science skills and content knowledge, venues that offer more opportunities for experimentation and exploration can promote deeper understandings. In this article I explore the background of science learning and venues where this learning can take place followed by a review of the benefits and necessary components of well designed immersive informal programs.

physics.ed-ph↗

arXiv2003

STIS spectroscopy of the emission line gas in the nuclei of nearby FR-I galaxies

We present the results of the analysis of a set of medium resolution spectra, obtained by the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, of the emission line gas present in the nuclei of a complete sample of 21 nearby, early-type galaxies with radio jets (the UGC FR-I Sample). For each galaxy nucleus we present spectroscopic data in the region of H-alpha and the dervived kinematics. We find that in 67% of the nuclei the gas appears to be rotating and, with one exception, the cases where rotation is not seen are either face on or have complex central morphologies. We find that in 62% of the nuclei the fit to the central spectrum is improved by the inclusion of a broad component. The broad components have a mean velocity dispersion of 1349 +/- 345 km\s and are redshifted from the narrow line components (assuming an origin in H-alpha) by 486 +/- 443 km\s.

astro-ph↗

arXiv2002

Gas Kinematics and the Black Hole Mass at the Center of the Radio Galaxy NGC 4335

(abridged) We investigate the kinematics of the central gas disk of the radio-loud elliptical galaxy NGC 4335, derived from HST/STIS long-slit spectroscopic observations of Halpha+[NII] along 3 parallel slit positions. The observed mean velocities are consistent with a rotating thin disk. We model the gas disk in the customary way. This sets a 3 sigma upper limit of 10^8 Msun on black hole mass, Mbh. The velocity dispersion at r <0.5'' is in excess of that predicted by the thin rotating disk model. This does not invalidate the model, if the excess dispersion is caused by localized turbulent motion in addition to bulk circular rotation. However, if instead the dispersion is caused by the BH potential then a mass Mbh ~ 6x10^8 Msun is inferred by modeling the central gas dispersion as due to an isotropic spherical distribution of collisionless gas cloudlets. The stellar kinematics for NGC 4335 are derived from a ground-based (WHT/ISIS) long-slit observation along the galaxy major axis. A two-integral model of the stellar dynamics yields Mbh >= 3x10^9 Msun. However, there is reason to believe that this model overestimates Mbh. Reported correlations between black hole mass and inner stellar velocity dispersion sigma predict Mbh to be >= 5.4x10^8 Msun in NGC 4335. If our standard thin disk modeling of the gas kinematics is valid, then NGC 4335 has an unusually low Mbh for its velocity dispersion. If, on the other hand, this approach is flawed, and provides an underestimate of Mbh, then black hole masses for other galaxies derived from HST gas kinematics with the same assumptions should be treated with caution.

astro-ph↗