26 research outputs found
Buried Black Hole Growth in IR-selected Mergers: New Results from Chandra
Observations and theoretical simulations suggest that a significant fraction
of merger-triggered accretion onto supermassive black holes is highly obscured,
particularly in late-stage galaxy mergers, when the black hole is expected to
grow most rapidly. Starting with the Wide-Field Infrared Survey Explorer
all-sky survey, we identified a population of galaxies whose morphologies
suggest ongoing interaction and which exhibit red mid-infrared colors often
associated with powerful active galactic nuclei (AGNs). In a follow-up to our
pilot study, we now present Chandra/ACIS and XMM-Newton X-ray observations for
the full sample of the brightest 15 IR-preselected mergers. All mergers reveal
at least one nuclear X-ray source, with 8 out of 15 systems exhibiting dual
nuclear X-ray sources, highly suggestive of single and dual AGNs. Combining
these X-ray results with optical line ratios and with near-IR coronal emission
line diagnostics, obtained with the near-IR spectrographs on the Large
Binocular Telescope, we confirm that 13 out of the 15 mergers host AGNs, two of
which host dual AGNs. Several of these AGNs are not detected in the optical.
All X-ray sources appear X-ray weak relative to their mid-infrared continuum,
and of the nine X-ray sources with sufficient counts for spectral analysis,
eight reveal strong evidence of high absorption with column densities of
~cm. These observations demonstrate that a
significant population of single and dual AGNs are missed by optical studies,
due to high absorption, adding to the growing body of evidence that the epoch
of peak black hole growth in mergers occurs in a highly obscured phase.Comment: 29 pages, 22 figures; (Main text: 17 pages, 4 figures
Interprofessional Healthcare Education, Research and Practice
Background
• What we ‘know’
– Literature identifies demonstrated change in attitudes as a result of learning with, about and from each other (Barr, et.al., 2000)
– Similar experiences at UK
• Less understood:
– What if students are required to participate if the primary motivation of the experience is not IPE?
– What does the process of interprofessional development look like?
• Relevant vectors for IPE
– Clinical is idea
– Consider global health as an appropriate contex
NuSTAR Observations of Four Mid-IR Selected Dual AGN Candidates in Galaxy Mergers
Mergers of galaxies are a ubiquitous phenomenon in the Universe and represent
a natural consequence of the ``bottom-up'' mass accumulation and galaxy
evolution cosmological paradigm. It is generally accepted that the peak of AGN
accretion activity occurs at nuclear separations of kpc for major
mergers. Here we present new NuSTAR and XMM-Newton observations for a subsample
of mid-IR preselected dual AGN candidates in an effort to better constrain the
column densities along the line-of-sight for each system. Only one dual AGN
candidate, J0841+0101, is detected as a single, unresolved source in the
XMM-Newton and NuSTAR imaging, while the remaining three dual AGN candidates,
J0122+0100, J1221+1137, and J1306+0735, are not detected with NuSTAR; if these
non-detections are due to obscuration alone, these systems are consistent with
being absorbed by column densities of log()
24.9, 24.8, and 24.6, which are roughly consistent with previously inferred
column densities in these merging systems. In the case of J0841+0101, the
analysis of the 0.3-30 keV spectra reveal a line-of-sight column density of
cm, significantly larger than the column
densities previously reported for this system and demonstrating the importance
of the higher signal-to-noise XMM-Newton spectra and access to the keV
energies via NuSTAR. Though it is unclear if J0841+0101 truly hosts a dual AGN,
these results are in agreement with the high obscuring columns expected in AGNs
in late-stage mergers.Comment: 21 pages, 9 tables, 4 figures. Accepted for publication in Ap
The Messy Nature of Fiber Spectra: Star-Quasar Pairs Masquerading as Dual Type 1 AGNs
Theoretical studies predict that the most significant growth of supermassive
black holes occurs in late-stage mergers, coinciding with the manifestation of
dual active galactic nuclei (AGNs), and both major and minor mergers are
expected to be important for dual AGN growth. In fact, dual AGNs in minor
mergers should be signposts for efficient minor merger-induced SMBH growth for
both the more and less massive progenitor. We identified two candidate dual
AGNs residing in apparent minor mergers with mass ratios of 1:7 and
1:30. SDSS fiber spectra show broad and narrow emission lines in the
primary nuclei of each merger while only a narrow [O III] emission line and a
broad and prominent H/[N II] complex is observed in the secondary
nuclei. The FWHMs of the broad H lines in the primary and secondary
nuclei are inconsistent in each merger, suggesting that each nucleus in each
merger hosts a Type 1 AGN. However, spatially-resolved LBT optical spectroscopy
reveal rest-frame stellar absorption features, indicating the secondary sources
are foreground stars and that the previously detected broad lines are likely
the result of fiber spillover effects induced by the atmospheric seeing at the
time of the SDSS observations. This study demonstrates for the first time that
optical spectroscopic searches for Type 1/Type 1 pairs similarly suffer from
fiber spillover effects as has been observed previously for Seyfert 2 dual AGN
candidates. The presence of foreground stars may not have been clear if an
instrument with more limited wavelength range or limited sensitivity had been
used.Comment: 15 pages including appendix and references, 6 figures, 1 table.
Accepted for publication in Ap
Multi-wavelength observations of SDSS J105621.45+313822.1, a broad-line, low-metallicity AGN
In contrast to massive galaxies with Solar or super-Solar gas phase
metallicities, very few Active Galactic Nuclei (AGN) are found in
low-metallicity dwarf galaxies. Such a population could provide insight into
the origins of supermassive black holes. Here we report near-infrared
spectroscopic and X-ray observations of SDSS J105621.45+313822.1, a low-mass,
low-metallicity galaxy with optical narrow line ratios consistent with star
forming galaxies but a broad H line and mid-infrared colors consistent
with an AGN. We detect the [Si VI] 1.96m coronal line and a broad
Pa line with a FWHM of ~km~s. Together with the
optical broad lines and coronal lines seen in the SDSS spectrum, we confirm the
presence of a highly accreting black hole with mass ~M, with a bolometric luminosity of
~erg~s based on the coronal line luminosity, implying a
highly accreting AGN. Chandra observations reveal a weak nuclear point source
with ~erg~s,
orders of magnitude lower than that predicted by the mid-infrared
luminosity, suggesting that the AGN is highly obscured despite showing broad
lines in the optical spectrum. The low X-ray luminosity and optical narrow line
ratios of J1056+3138 highlight the limitations of commonly employed diagnostics
in the hunt for AGNs in the low metallicity low mass regime.Comment: 13 pages, 6 figures, accepted to Ap
Nuclear Activity in the Low Metallicity Dwarf Galaxy SDSS J0944-0038: A Glimpse into the Primordial Universe
Local low metallicity dwarf galaxies are relics of the early universe and
hold clues into the origins of supermassive black holes (SMBHs). In recent
work, coronal lines have been used to unveil a population of candidate
accreting black holes in dwarf galaxies with gas phase metallicities and
stellar masses well below the host galaxies of any previously known AGNs. Using
MUSE/VLT observations, we report the detection of [Fe X] 6374 coronal
line emission and a broad H line in the nucleus of SDSS
J094401.87003832.1, a nearby () metal poor dwarf galaxy at least
fifty times less massive than the LMC. The [Fe X] 6374 emission is
compact and centered on the brightest nuclear source, with a spatial extent of
100 pc. The [Fe X] luminosity is erg s,
within the range seen in previously identified AGNs in the dwarf galaxy
population. This line has never been observed in gas ionized by hot stars.
While it can be produced in supernova ejecta, the [Fe X] flux from SDSS
J094401.87003832.1 has persisted over the ~19 year time period between the
SDSS and MUSE observations, ruling out supernovae as the origin for the
emission. The FWHM of the broad component of the H line is
km s and its luminosity is erg s,
lower than the broad line luminosities of previously identified low mass broad
line AGNs. These observations, together with previously reported
multi-wavelength observations, can most plausibly be explained by the presence
of an accreting intermediate mass black hole in a primordial galaxy analog.
However, we cannot rule out the possibility that current stellar population
models of metal poor stars significantly under-predict the stellar ionizing
photon flux, and that metal poor stars can produce an extreme ionizing spectrum
similar to that produced by AGNs.Comment: 12 pages, 5 figures, 1 table, submitted to ApJL. Comments welcom
Forward Thinking and Adaptability to Sustain and Advance IPECP in Healthcare Transformation Following the COVID-19 Pandemic
The proliferation of the novel SARS-CoV-2 (COVID-19) virus across the globe in 2020 produced a shared trauma internationally of unprecedented devastation, disruption, and death. At the same time, the pandemic has been a transformation catalyst accelerating the implementation and adoption of long overdue changes in healthcare education and practice, including telehealth and virtual learning. The COVID-19 pandemic has placed healthcare at a crossroads, either viewing it as a temporary situation that requires short-term solutions, or as a major disruption that presents opportunities for innovation for sustainable development and transformation. As COVID-19 transitions from pandemic to endemic, we have a unique opportunity to leverage lessons learned that can foster healthcare transformation through innovation, forward thinking, and interprofessional education and collaborative practice (IPECP). With the changing landscape of higher education and healthcare, IPECP leaders need to reflect on and implement ‘Forward Thinking and Adaptability’ and ‘Sustainability and Growth’ in their IPECP approaches and strategies to achieve the Quintuple Aim. To capitalize on this opportunity and based on a recent publication by InterprofessionalResearch Global, this paper explores and debates (from a global perspective) the impact and application of healthcare education and practice transformation on IPECP with the goal to identify best practices in integrating and sustaining IPECP and building a resilient workforce
LEM All-Sky Survey: Soft X-ray Sky at Microcalorimeter Resolution
The Line Emission Mapper (LEM) is an X-ray Probe with with spectral
resolution ~2 eV FWHM from 0.2 to 2.5 keV and effective area >2,500 cm at 1
keV, covering a 33 arcmin diameter Field of View with 15 arcsec angular
resolution, capable of performing efficient scanning observations of very large
sky areas and enabling the first high spectral resolution survey of the full
sky. The LEM-All-Sky Survey (LASS) is expected to follow the success of
previous all sky surveys such as ROSAT and eROSITA, adding a third dimension
provided by the high resolution microcalorimeter spectrometer, with each 15
arcsec pixel of the survey including a full 1-2 eV resolution energy spectrum
that can be integrated over any area of the sky to provide statistical
accuracy. Like its predecessors, LASS will provide both a long-lasting legacy
and open the door to the unknown, enabling new discoveries and delivering the
baseline for unique GO studies. No other current or planned mission has the
combination of microcalorimeter energy resolution and large grasp to cover the
whole sky while maintaining good angular resolution and imaging capabilities.
LASS will be able to probe the physical conditions of the hot phases of the
Milky Way at multiple scales, from emission in the Solar system due to Solar
Wind Charge eXchange, to the interstellar and circumgalactic media, including
the North Polar Spur and the Fermi/eROSITA bubbles. It will measure velocities
of gas in the inner part of the Galaxy and extract the emissivity of the Local
Hot Bubble. By maintaining the original angular resolution, LASS will also be
able to study classes of point sources through stacking. For classes with
~ objects, it will provide the equivalent of 1 Ms of high spectral
resolution data. We describe the technical specifications of LASS and highlight
the main scientific objectives that will be addressed. (Abridged)Comment: White Paper in support of a mission concept to be submitted for the
2023 NASA Astrophysics Probes opportunity. This White Paper will be updated
when required. 30 pages, 25 figure
BASS XXXIV: A Catalog of the Nuclear Mm-wave Continuum Emission Properties of AGNs Constrained on Scales 100--200 pc
We present a catalog of the millimeter-wave (mm-wave) continuum properties of
98 nearby ( 0.05) active galactic nuclei (AGNs) selected from the 70-month
Swift/BAT hard X-ray catalog that have precisely determined X-ray spectral
properties and subarcsec-resolution ALMA Band-6 (211--275 GHz) observations as
of 2021 April. Due to the hard-X-ray ( 10 keV) selection, the sample is
nearly unbiased for obscured systems at least up to Compton-thick-level
obscuration, and provides the largest number of AGNs with high physical
resolution mm-wave data ( 100--200 pc). Our catalog reports emission
peak coordinates, spectral indices, and peak fluxes and luminosities at 1.3 mm
(230 GHz). Additionally, high-resolution mm-wave images are provided. Using the
images and creating radial surface brightness profiles of mm-wave emission, we
identify emission extending from the central source and isolated blob-like
emission. Flags indicating the presence of these emission features are
tabulated. Among 90 AGNs with significant detections of nuclear emission, 37
AGNs ( 41%) appear to have both or one of extended or blob-like
components. We, in particular, investigate AGNs that show well-resolved mm-wave
components and find that these seem to have a variety of origins (i.e., a jet,
radio lobes, a secondary AGN, stellar clusters, a narrow line region, galaxy
disk, active star-formation regions, and AGN-driven outflows), and some
components have currently unclear origins.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ