2021 APO Science Symposium - held virtually on July 26-28, 2021
The APO Science Symposium highlights scientific and/or educational results from the ARC 3.5m and/or ARCSAT telescopes.
Jump to Monday's talks, Tuesday's talks, or Wednesday's talks.
science theme: Stars
schedule: Mon, 10:00 - 10:15 MDT |
video (youtube)
Brett Morris
Universität Bern
Exoplaneteers and stellar atmosphere enthusiasts alike can agree on at least one thing: knowing the phase and strength of a star's activity cycle is valuable information which can only be gained through long-term, continuous monitoring from mid-sized observatories like APO. In this observing program, we have created a legacy survey of exoplanet-host star Ca II H & K emission line observations extending into the distant future with APO/ARCES, which we call the Olin Wilson Legacy Survey (OWLS). We also include many stars from the original Mt. Wilson survey to extend the monitoring baseline by decades. The time-series database of Ca II H & K measurements will be a touchstone reference to determine the extent of contamination by stellar activity in exoplanet observations, as well as a modern update to the Baliunas et al. (1995) Mt. Wilson survey (started by Olin Wilson) which reveals how the magnetic activity of solar type stars varies with spectral type, rotation period, planet orbital period, etc.
science theme: Stars
schedule: Mon, 10:15 - 10:30 MDT |
video (youtube)
John Bally
University of Colorado
ARCTIC and NICFPS narrow-band imaging and APO spectroscopy were used to study massive star and cluster formation in the Solar vicinity and in some nearby galaxies. Although most forming stars produce jets and bipolar outflows during birth, some drive powerful explosions which are sufficiently luminous in the IR to be seen in nearby galaxies. Orion OMC1 is the prime example where a 10^48 erg explosion occurred ~550 years ago. Highly supersonic, `Hubble Law’ expansion of nebular plasma in the young, bipolar HII region, Sh2-106, indicates that it also experienced an explosion ~4,000 years ago. Several other Galactic candidates have been found including DR21 and G5.89-0.39. Such explosions may be driven by major accretion bursts, 3- and 4-body interactions in compact groups and clusters, and by N-body integrations resulting in protostellar mergers. Though the signatures of explosions are short-lived, explosions and dynamical ejection of stars from their birth sites by N-body processes provide powerful feedback mechanisms in the self-regulation of star formation, may prevent further stellar growth, and contribute to establishing the IMF.
science theme: Stars
schedule: Mon, 10:30 - 10:45 MDT |
video (youtube)
Henrique Reggiani
Johns Hopkins University
The existence of hypervelocity stars was proposed by Hills (1988), but their existence continued a mystery for ~20 years. Brown et al. (2005) identified a star with a total velocity of 853 km/s, unbound from the galactic potential. After this initial discovery, the interest around these objects grew and theories predicting mechanisms to accelerate stars were put forward. These include ejection from a binary system when one star goes supernovae, tidal debris from a dwarf galaxy recently disrupted, dynamical ejection from stellar clusters, ejection from star-forming dwarfs, etc. However, before 2018 we only had identified ~20 hypervelocity stars, all of which were massive and young. After Gaia we identified several more extreme velocity stars. More importantly, we identified extreme velocity late-type stars. Late-type stars can be chemically characterized, helping us identify where these stars formed, and therefore their acceleration mechanism. Up until now only 4 of such stars have been followed up with spectroscopy and their chemistry indicate they are the tail of the velocity distribution of the galactic halo. In this talk we will show a chemical analysis of 15 new hypervelocity stars, which will help us constrain their acceleration mechanism.
science theme: Stars
schedule: Mon, 10:45 - 11:00 MDT |
video (youtube)
Jason Jackiewicz
New Mexico State University
The ARC 3.5m telescope and its ARCES spectrograph have been, and will continue to be powerful tools for studying diverse binary star systems. In particular, when coupled with high-precision photometric observations, the spectra are invaluable for providing insights into pulsating stars, eclipsing systems, spectroscopic binaries, stellar evolution, rotation and magnetic fields, among many other stellar astrophysics areas. We will highlight some of the interesting discoveries of the past five years from a group at NMSU and collaborators who have obtained excellent data from this facility, and discuss what is still to be learned.
science theme: AGN
schedule: Mon, 11:15 - 11:30 MDT |
video (youtube)
Donald Terndrup
Ohio State University
Temporal variability in the broad absorption lines of Markarian 231
Maria Pudoka (1) Luca Schmitt (1) Donald M. Terndrup (1, 2) Hyunseop Choi (2) Karen M. Leighly (2)
(1) Department of Astronomy, The Ohio State University (2) Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma
Markarian 231 is a nearby (z = 0.0421) Seyfert I galaxy which is ultraluminous at infrared wavelengths. Its spectrum shows strong broad absorption complexes at optical wavelengths from Na I and Ca II, and in both optical and infrared wavelengths from metastable He I.
Since 2017, we have used moderate-resolution (R ~ 2500) spectra from APO and the MDM Observatory to explore temporal changes in the strength and velocities of these absorption features. We discuss the observed phenomenology of line variability, paying special attention to issues of spectral resolution and wavelength calibration, and show that the velocity of one outflow component has slowed significantly. We also discuss progress on speed improvements to our quasar spectral-synthesis program SimBAL.
science theme: AGN
schedule: Mon, 11:30 - 11:45 MDT |
video (youtube)
Justin Robinson
Georgia State University
It has become apparent in the past two decades that supermassive black holes (SMBHs) and their host galaxies have a symbiotic relationship. SMBHs scale with several large-scale galaxy properties, and the general interpretation of these scaling relationships is that SMBH-galaxy growth is regulated by the feedback from active galactic nuclei (AGNs). These relationships allow insight into galaxy-black hole behavior over cosmic time, therefore it is vital to obtain accurate measurements of the galaxy properties that scale with the central SMBHs. One of the largest known uncertainties in SMBH-galaxy scaling relations is the lack of accurate distances to AGN host galaxies. Almost all distances to active galaxies in the local universe are estimated from redshift, and therefore may be heavily affected by the local peculiar velocity field and subsequently produce large uncertainties in galaxy properties that directly rely on distance (e.g., luminosity). Thus, I will discuss our Tully-Fisher-based distance measurements to a sample of nearby AGN host galaxies. These measurements combine HI 21cm emission and optical imaging, including observations with the ARC 3.5m and ARCSAT telescopes.
science theme: AGN
schedule: Mon, 11:45 - 12:00 MDT |
video (youtube)
Beena Meena
Georgia State University
We present an in-depth study of AGN driven outflows in the narrow-line regions of Seyfert galaxies using spectroscopic and imaging observations from APO’s ARC 3.5m telescope and Hubble Space Telescope. First, we measure the kinematics of the AGN ionized gas using spatially-resolved emission lines, and determine the extents of the outflows. Then, we perform a 2D surface brightness decomposition using GALFIT on high resolution HST and APO images to identify different morphological components of the host galaxies and their stellar mass distributions. Finally, we solve for the launch distances of the observed outflows using a radiative acceleration-gravitational deceleration model. By expanding this analysis over a sample of nearby targets, we can derive whether the outflows sizes and their launch distances scale with the AGN properties such as the supermassive black hole masses and luminosities.
science theme: AGN
schedule: Mon, 12:00 - 12:15 MDT |
video (youtube)
Moire Prescott
New Mexico State University
A rare sample of spatially extended emission line nebulae at z~0.3, nicknamed "Green Beans", was discovered in SDSS imaging thanks to strong [OIII] emission. Subsequent evidence suggested that these nebulae may be associated with recently faded AGN and that they are local cousins of the Lyman-alpha (Lya) nebulae found at high redshift. We are using follow-up APO/DIS spectroscopy to better understand these low-z Lya nebulae and how they compare to other strong emission line sources. Our spectroscopic data has shown that low-z Lya nebulae have emission line ratios, line widths, sizes, and kinematics that resemble other Type 2 AGN at the same redshift, confirming that they are powered by Type 2 AGN with typical ionizing continua. Low-z Lya nebula systems may be drawn from the high luminosity end of the Type 2 AGN distribution, with higher nuclear activity driving high [OIII] equivalent widths and more central star formation leading to bluer optical continua. By studying these low-z Lya nebulae, we can better understand the conditions associated with a rapid ramp-down in AGN ionizing output as well as their relationship with the Lya nebula population at high redshift.
science theme: Instrumentation
schedule: Mon, 13:00 - 13:15 MDT |
video (youtube)
Sarah Tuttle
University of Washington
After being decommissioned at the Mayall 4m on Kitt Peak, the KOSMOS spectrograph has been undergoing an upgrade in our University of Washington lab. I'll present the basic characteristics of KOSMOS @ APO, discuss the upgrades (including a new slitviewer), and update our status towards (re)commissioning. KOSMOS @ APO will bring updated low resolution single and multi-object optical spectroscopic coverage to the 3.5m for many years to come.
science theme: Instrumentation
schedule: Mon, 13:15 - 13:30 MDT |
video (youtube)
Debby Tran
University of Washington
KOSMOS is a low-resolution, long-slit, optical spectrograph currently being retrofitted at the University of Washington for its move from Kitt Peak National Observatory to Apache Point Observatory. One of the additions to KOSMOS is a slit viewer, which requires the fabrication of new reflective slits, as KOSMOS previously used matte slits machined via wire EDM (electrical discharge machining). We test a novel method of slit fabrication using nanofabrication methods and compared the roughness and width uniformity of the reflective and matte slits. Overall, the chemically-etched reflective slits are smoother than the machined matte slits by roughly an order of magnitude, an average of ~0.3 micron versus ~1 micron residuals respectively, as well as more consistent in width, with width standard deviation of less than or equal to 13 microns versus 21 microns respectively. Future work will consist of testing and comparing the performance of these more uniform, smoother slits to the matte slits.
science theme: Instrumentation
schedule: Mon, 13:30 - 13:45 MDT |
video (youtube)
Kal Kadlec
University of Washington
ARCTIC is an instrument on the ARC 3.5m telescope that is capable of providing a diffuser-assisted photometrically precise image. The instrument has a diffuser that is inserted into the optical path to produce a 3-4 times broader and a more stable top-hat shaped point spread function. Currently the stationary diffuser is simply inserted into the optical path. To provide better photometric performance, a diffuser rotation of 120-180 rpm is proposed to increase photometric precision by further increasing the diffusion of light. The Telescope Engineering Group (TEG) at the University of Washington is working towards delivering the upgraded diffuser assembly to the observatory. The new design also incorporates upgrades in functionality to aid in operation and safety.
science theme: Instrumentation
schedule: Mon, 13:45 - 14:00 MDT |
video (youtube)
Derek Buzasi
Florida Gulf Coast University
We discuss the expansion of the capabilities of the ARCSAT telescope to include spectroscopy. We have successfully mounted a commercial spectrograph, the Shelyak eShel, on the 0.5m telescope. This instrument is a fiber-fed single-object echelle spectrograph with R ~ 10,000 and wavelength coverage from Ca II H+K to approximately 7200 Å. In operation, the limiting magnitude in an 1800 s exposure is approximately V = 9. In this presentation, we illustrate the capabilities of the instrument, showing the user interface (still a work in progress), data reduction procedure, and some sample spectra. We anticipate that the spectrograph will become a facility instrument later this year.
science theme: Minor Bodies & Moons
schedule: Tue, 10:00 - 10:15 MDT |
video (youtube)
Adam McKay
American University/NASA Goddard Space Flight Center
Comets are primitive leftovers from the formation of the Solar System, making them key objects of study to constrain the physics and chemistry of the early Solar System. For the past decade we have been systematically observing comets with ARCES at APO in order to better understand their composition as well as the photochemistry occurring in their comae. We will present an overview of key results from our program. These include a multi-observatory campaign (including the Spitzer Space Telescope and the NEOWISE mission) to evaluate [OI] emission as a proxy for CO2 in comets and long temporal baseline observations to observe how cometary composition varies with time. We will also discuss results from two specific comets: the CO-dominated comet C/2016 R2 (PanSTARRS) and interstellar comet 2I/Borisov, for which ARCES observations provided the earliest reported detection of a water tracer in this unique object. We will also discuss future plans, including the upcoming apparition of Rosetta target comet 67P/Churyumov-Gerasimenko.
science theme: Minor Bodies & Moons
schedule: Tue, 10:15 - 10:30 MDT |
video (youtube)
David DeColibus
New Mexico State University
Miranda, the smallest and innermost classical satellite of Uranus, is an enigmatic icy moon which has only been examined up-close once with the Voyager 2 flyby in 1986. Miranda is too small to maintain geological activity over the age of the Solar System, but the Voyager images show apparent evidence of large-scale geological modification <1 Ga. No new missions are currently planned to visit the Uranian system, so telescopic observations are the only method of continued study of the Uranian moons. Near-infrared spectroscopy shows that the surfaces of the Uranian satellites are primarily composed of water ice, but closer inspection reveals spatial trends in surface composition. The four larger Uranian satellites all show an asymmetry in the strength of their water ice absorption features between their leading and trailing hemispheres. This longitudinal asymmetry is expected to be strongest on Miranda, but Miranda shows little to no evidence of this asymmetry. We therefore undertook an extensive observing campaign with the ARC 3.5m and the TripleSpec NIR spectrograph to study how the strength of water ice absorption features vary with longitude on Miranda, and discuss potential implications for the processes modifying Miranda's surface.
science theme: Minor Bodies & Moons
schedule: Tue, 10:30 - 10:45 MDT |
video (youtube)
Mikhail Sharov
Boston University
Io’s sulfur dioxide atmosphere is very sensitive to variations in its surface temperature. As Io passes into Jupiter’s shadow its sublimation-supported atmosphere rapidly collapses, leaving volcanic outgassing as the sole component supporting the atmosphere. Ground-based optical observations of Io-in-eclipse are difficult, as they require precise timing and non-sidereal blind tracking with high accuracy. Using the 3.5m ARC Echelle Spectrograph, we regularly observe Io’s atomic emissions surrounding eclipse. In shadow, electron impact and ion recombination excite red line oxygen (6300Å) and the sodium D doublet aurora at brightness levels of several kiloRayleighs. Despite the SO2 collapse, we find that oxygen is non-responsive to eclipse. However, oxygen emission does vary rapidly and is correlated with the geometry of the Io plasma torus. This behavior is consistent with our HST-FUV observations and offers insight to the electron flux incident upon Io’s upper atmosphere. Unexpectedly, we find that sodium exhibits both a rapid decrease at ingress, and a brightening following egress on timescales of only 10s of minutes. We attribute this to the interruption of the NaCl+ production channel in shadow. APO measurements of Io-in-eclipse directly quantify its atmospheric photochemical lifetimes, and help disentangle the complex interaction of this volcanic moon and Jupiter’s magnetosphere.
science theme: Minor Bodies & Moons
schedule: Tue, 10:45 - 11:00 MDT |
video (youtube)
Nancy Chanover
New Mexico State University
The ARC 3.5m telescope at Apache Point Observatory has been operating continuously since 2006 as the premier US-based lunar laser ranging (LLR) facility. With consistent operations and a number of improvements over the past 15 years, we routinely achieve measurements of the Moon’s orbital position to millimeter precision. Such measurements enable fundamental tests of gravity, including tests of the strong equivalence principle, the time-rate-of-change of Newton’s gravitational constant, gravitomagnetism, the inverse-square law, as well as studies of the Earth-Moon system, including the gravitational interaction between the two bodies, the lunar interior, and Earth geodesy. We discuss future plans for the lunar laser ranging experiment at APO, which will enable NASA to maintain preeminence in the LLR arena and prepare for further advances that will be enabled by the installation of the Next Generation Lunar Retroreflectors.
science theme: Suns & Planets
schedule: Tue, 11:15 - 11:30 MDT |
video (youtube)
Derek Buzasi
Florida Gulf Coast University
The star we know best is the one which is closest to us, the Sun, and improving our understanding of our star is an important goal for astrophysics in general. One approach to this problem focuses on the study of solar analogs, stars which are like the Sun and thus might shed light on characteristics of its composition, structure, activity, planetary system, evolution, and future. While statistical considerations would lead us to prefer the largest sample size possible, we still lack a large, coherent, consistent sample of solar analogs.
We have used the K2 mission archive as an input to building such a sample, starting with approximately 2000 photometrically-selected analogs. K2 has the advantage of combining exquisite photometric precision, relatively long observing windows, and a selection of broadly distributed fields near the ecliptic plane. For each candidate, we measured photometric activity levels and rotation periods using K2 light curves, distances and improved colors using Gaia, and chromospheric/coronal activity diagnostics with Chandra and GALEX. The best candidates were selected for follow-up with the APO 3.5-meter ARCES instrument to determine metallicities and consistent estimates of RHK’ indices. In this presentation, I show the work in progress.
science theme: Suns & Planets
schedule: Tue, 11:30 - 11:45 MDT |
video (youtube)
Sarah Kovac
New Mexico State University
Formation and evolution are key topics in planetary science, and we cannot fully understand planetary atmospheres without accounting for their interactions with the solar wind. The presence of aurora is an important manifestation and tracer of the interaction between the solar wind and planetary ionospheres. The OI (1S-1D) 557.7 nm (oxygen green line) is a bright auroral line in the terrestrial atmosphere and is detected on the Venusian nightside after major solar storms. Currently, the processes responsible for producing the green line emission on Venus are poorly understood, yet the observed variability of this feature is clearly linked to the solar wind environment. Here, we use the Wang-Sheeley-Arge (WSA) model and in situ data from Parker Solar Probe (PSP) to look at the solar wind conditions during a detection of the Venusian green line on 11 July 2020, when PSP was making its closest approach to Venus.
science theme: Suns & Planets
schedule: Tue, 11:45 - 12:00 MDT |
video (youtube)
Emma Dahl
New Mexico State University
Both the identity of the coloring agents in Jupiter's atmosphere and the exact structure of Jupiter's uppermost cloud deck are yet to be conclusively understood. While the arrival of the Juno spacecraft at Jupiter in July 2016 has since recontextualized the Jovian system, Juno's optical camera lacks the spectral resolution necessary to probe the altitude and structure of the uppermost cloud deck and the identity of the coloring agent in Jupiter’s troposphere. As part of an international ground-based observing campaign in support of the Juno mission, we have used the New Mexico State University Acousto-optic Imaging Camera (NAIC) at the 3.5-m telescope at Apache Point Observatory in Sunspot, NM to capture optical hyperspectral image cubes of Jupiter whenever Juno completed a close perijove pass of the planet and viewing geometry allowed. These data were then used to test a parameterization of Jupiter's clouds called Crème Brûlée model, which presumes that a single chromophore is present in a thin layer above the uppermost cloud deck in varied amounts, lending Jupiter its diverse reddish hues. We found that the Crème Brûlée model is a valid parameterization of Jupiter’s troposphere, but that a different model might be necessary for unique weather events.
science theme: Time Domain Astronomy
schedule: Tue, 13:00 - 13:15 MDT |
video (youtube)
Keaton Bell
University of Washington
The vast majority of stars host exoplanets, and the vast majority of stars conclude their evolution as roughly Earth-sized white dwarf stars; therefore, we expect the majority of white dwarfs to host exoplanets. Searching for exoplanet transits of white dwarfs requires different considerations than other areas of exoplanet research, since the compact stars in this case can be totally eclipsed by larger planets. I detail the observational properties of such transits, demonstrate that multiple transits of white dwarfs are likely buried in our current volume of ground-based survey photometry, and share my current approaches to uncovering these systems in public Zwicky Transient Facility data. In particular, I highlight the ongoing photometric and spectroscopic follow-up efforts using the Agile and DIS instruments on the ARC 3.5-meter at Apache Point Observatory.
science theme: Time Domain Astronomy
schedule: Tue, 13:15 - 13:30 MDT |
video (youtube)
James DerKacy
University of Oklahoma
We present early optical and UV analysis of Type Ia supernova SN 2021fxy. Our data set includes ground-based photometry starting within a day of discovery and detailed spectroscopic follow-up including HST/STIS UV spectroscopy, extending through the optical (including several spectra taken with the APO 3.5m telescope) through the near-infrared. SN 2021fxy is similar in nature to SN 2017erp, including nearly identical UV spectra, albeit with a "shallow-silicon" sub- classification in comparison to SN 2017erp's "core-normal" designation. SN 2021fxy also shows persistent high-velocity Ca II features as well as additional structure within the Si II 6355 line profile. Early observations of all types of supernovae are the key to understanding the nature of the progenitor systems and explosion mechanisms. The observational coverage of SN 2021fxy highlight the methodology of the Precision Observations of Infant Supernovae Experiment (POISE), whose first run spanned 80 nights on the SWOPE telescope at LCO, with followup provided by a suite of telescopes around the world including APO. POISE will have a second run beginning in October 2021.
science theme: Time Domain Astronomy
schedule: Tue, 13:30 - 13:45 MDT |
video (youtube)
Melissa Graham
University of Washington
The Zwicky Transient Facility (ZTF) is an optical wide-field time-domain survey. The public component of this survey releases alerts about its discoveries worldwide in real time. The University of Washington has been working primarily with the ZTF "Redshift Completeness Factor" (RCF) team, which aims to spectroscopically classify all publicly announced transients that peak at r < 18 mag. This talk will present the role of APO and DIS observations in the RCF and a few science results enabled by APO+DIS.
science theme: Time Domain Astronomy
schedule: Tue, 13:45 - 14:00 MDT |
video (youtube)
Eric Bellm
University of Washington
The high availability and quick instrument changes possible with the 3.5m make it an excellent observatory for Target of Opportunity followup of time-sensitive events. These capabilities are particularly well-matched to events discovered by Zwicky Transient Facility (ZTF), which surveys the Northern Hemisphere Sky to depths of ~20.5 mag every 2-3 nights. Since 2018 we have conducted a TOO program to follow up ZTF events--but in practice this program has rarely been triggered. I will discuss a range of factors which have contributed to this lack of utilization, and implications for time-domain followup in the era of the Vera C. Rubin Observatory.
science theme: Quasars
schedule: Wed, 10:00 - 10:15 MDT |
video (youtube)
Hyunseop Choi
University of Oklahoma
Iron low-ionization broad absorption-line quasars (FeLoBALQs) show unambiguous spectral signatures of powerful quasar outflows that could potentially power quasar feedback. Although they were discovered more than several decades ago, only a small number of FeLoBALQs have been studied in detail because they show complex spectral features that are extremely challenging to analyze. Our group has developed a novel forward-modeling software package called SimBAL that uses a Bayesian model calibration method to model BALQ spectra. Using this, we discovered the most energetic quasar outflow known to date in the z = 2.264 quasar SDSS J135246.37+423923.5 (Choi et al. 2020); key to this discovery was an accurate redshift measured with TripleSpec. We have analyzed spectra of 50 low-redshift FeLoBALQs and constrained the outflow properties using SimBAL to systematically investigate the properties of the FeLoBALQ outflow. Furthermore, we analyzed the spectral energy distribution and optical properties of a subsample of 30 z<1 objects to measure the black hole mass and accretion properties. We found that the FeLoBAL outflows are located at a wide range of distances ranging from parsec to kiloparsec scales from the central engine. We also discovered evidence for two distinct populations within the FeLoBALQs.
science theme: Quasars
schedule: Wed, 10:15 - 10:30 MDT |
video (youtube)
Sofia Pasquini
The University of Western Ontario
We are studying absorption variability in an unusual variable Iron (Fe) Low-Ionization broad absorption line quasar (FeLoBALQ), SDSS J122933.32+262131.2. A dynamical model for such an outflow would be a key component in understanding the nature of variability in these objects that could help clarify their impact on host galaxy evolution. Multi-epoch optical spectra were fit using the novel software package SimBAL to constrain the physical parameters of the outflow. Preliminary results indicate significant variability in ionization state and density of outflowing gas over 1.86 years in the quasar rest-frame and model extrapolation has predicted rare absorption in the Balmer lines. A TripleSpec spectrum obtained from the Apache Point Observatory confirmed the presence of these Balmer absorption features and the present O-III doublet was used to calibrate the redshift of this object to z=2.5941 ± 0.0002. We fit the H-alpha emission in order to constrain the mass of the central supermassive black hole and intend to use it further to derive its bolometric luminosity and mass accretion rate. These results add to the sample of FeLoBALQ variability studies and form the foundation of a large-scale dynamical model for this outflow.
science theme: Quasars
schedule: Wed, 10:30 - 10:45 MDT |
video (youtube)
Kolya Larson
The Ohio State University
Kolya Larson (1)
Donald M. Terndrup (1, 2)
Hyunseop Choi (2)
Karen M. Leighly (2)
(1) Department of Astronomy, The Ohio State University
(2) Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma
Quasars exhibit broadband temporal variability on many time scales, which poses a problem in the analysis of quasar spectra. Ultraviolet/optical/infrared photometry used to derive the spectral energy distribution (SED) may come from observations over many years and may not be contemporaneous with spectral observations. Furthermore, some quasars are extremely faint and so reported catalog magnitudes have large errors or are upper limits.
We have obtained optical/IR photometry of selected quasars in ugriz and JHK from APO and the MDM Observatory to fill gaps in the SED and to explore variability in photometric bands not covered by time-series surveys such as the Zwicky Transit Facility. We discuss the calibration of our photometry with emphasis on random and systematic errors, the latter mainly from uncertainty in color transformations. We demonstrate tools for exploring variability in individual objects and confirm that variability is most significant at shorter wavelengths. We finally discuss how APO could be used in future quasar surveys for SED mapping and variability studies.
science theme: Quasars
schedule: Wed, 10:45 - 11:00 MDT |
video (youtube)
Jessica Werk
University of Washington
We present a new sample of low-Galactic-latitude UV-bright QSOs spectroscopically confirmed with the APO 3.5-m. These sources fill a gap in the Galactic latitude coverage of the available samples of known UV-bright QSO background probes. We obtained low-dispersion, optical, longslit spectra with the APO 3.5-m for approximately 25% of our low-b QSO candidates and confirmed 73% (N = 60) as AGN with z < 1. Here, we demonstrate how high-resolution HST/COS follow-up spectroscopy of these new low-Galactic-latitude QSOs has the potential to transform our view of the Milky Way circumgalactic medium.
science theme: Active Stars
schedule: Wed, 11:15 - 11:30 MDT |
video (youtube)
Rachel Miller
University of Colorado
The merging of the blue hydrogen emission lines in solar and stellar flares is an invaluable diagnostic of the ionization of the chromosphere in response to impulsive heating. Previous studies with moderate-to-high resolving power in this spectral region have shown a variety of phenomena, ranging from a suggestive discontinuity to a smooth blackbody-like continuum that extends blueward of the Balmer limit at 3646 Å. To gain new insight into the emission line wing blending in M dwarf flares, we conducted high-cadence flare monitoring of the dM4.5e star YZ CMi using the B1200 grating of DIS on the ARC 3.5m at the Apache Point Observatory. Spectral data of the impulsive and gradual phases of a moderately sized flare were obtained on 17-11-26. Light curves were calculated for the prominent emission lines of Hγ, Hβ, Ca II H, Ca II K, and H8. We searched in detail for the presence or absence of a discontinuity in the continuum in the near-ultraviolet/blue region (λ = 3600-3800 Å). We find no evidence of any feature in the flare spectra, suggesting that there exists a pseudo-continuum of blended hydrogen lines. These data provide new constraints on the physical origin of the pseudo-continuum, which is included in radiative transfer models as an ad hoc "dissolved level" continuum opacity.
science theme: Active Stars
schedule: Wed, 11:30 - 11:45 MDT |
video (youtube)
Maria Schutte
University of Oklahoma
Understanding magnetic activity on the surface of planet-hosting stars other than the Sun since exoplanet analyses must include these effects to properly characterize the exoplanet’s atmosphere. Using data from the Apache Point Observatory’s 3.5-m ARC telescope with the ARCTIC instrument, we use the starspot modeling program STarSPot (STSP) to measure the position and size of a starspot for an M0 dwarf star (M = 0.661^{+0.025}_{-0.023} M_sun, R = 0.656^{+0.017}_{-0.016} R_sun) which has a transiting stellar companion (M8 dwarf). STSP employs a novel technique to measure the spot positions and radii by using the transiting secondary as a magnifying glass to probe down to less than 1% changes in the surface brightness of the star for high-precision photometry. We achieve high-precision ground-based photometry using the Engineered Diffuser available on the ARCTIC instrument. Preliminary results show the presence of a large starspot (radius of ~18% of the star) that appears to be present in multiple observations across months of time. This starspot is ~3x the size of typical solar maximum sunspots and sunspot groups even with the synchronous rotational period (0.998 +/- 0.001 days) and orbital period of the companion (0.999661 +/- 0.000002 days). This analysis is part of a larger ARCTIC program to characterize starspot properties using high-precision transiting exoplanet light curves across a range of spectral types and rotation rates, including a study of the temperature of starspots using simultaneous multi-filter observations.
This research is funded through NSF grants 1907622, 1909506, 1909682, 1910954.
science theme: Active Stars
schedule: Wed, 11:45 - 12:00 MDT |
video (youtube)
Yuta Notsu
University of Colorado
Flares are releases of magnetic energy in the stellar atmosphere, and they have strong emissions. During some M dwarf flares, chromospheric line profiles show blue asymmetries (e.g., Honda et al. 2018), although red asymmetries are more commonly observed in solar flares. Similar enhancements of the blue wings of Balmer lines may provide clues for investigating the early phases of stellar coronal mass ejections (CMEs) during flares (cf. Vida et al. 2016&2019), but this is still controversial. Then we have conducted simultaneous spectroscopic and photometric observations of mid M dwarf flare stars mainly using APO 3.5m/ARCES and ARCSAT. During 34 nights of observations, we detected 48 flares in Balmer lines (e.g. Hα). Among them, at least 7 flare events show clear blue asymmetries. Blue asymmetry durations are different among the 7 events (20min ~ 2hr). These results suggest upward flows of chromospheric plasma during flare events. By assuming that the blue asymmetries were caused by prominence eruptions, we estimate the mass and kinetic energy to be 10^15 - 10^18 g and 10^29 - 10^32 erg, respectively. The estimated masses are comparable to expectations from the empirical relation between the flare X-ray energy and mass for stellar flares and solar CMEs.
science theme: Active Stars
schedule: Wed, 12:00 - 12:15 MDT |
video (youtube)
Adam Kowalski
University of Colorado
The Balmer jump ratio is an important diagnostic of the optical depth over T~10,000 K in stellar flares. New radiative-hydrodynamic flare models show that large heating rates lead to 10,000 K blackbody-like radiation ("incandescence"), while smaller heating rates produce low optical depth and a large Balmer jump (recombination radiation). To test the wide range of these predictions, we made measurements of the Balmer jump ratio in a large sample of dMe flares using two narrowband blue continuum filters on ARCTIC with the ARC 3.5m at APO. I report on preliminary results from this multi-year campaign, which benefited from simultaneous monitoring with ARCSAT/Flarecam. I discuss how this expands our knowledge of stellar flare physics to regimes that have not been observed before, and I discuss the broader importance to other sub-fields, such as the study of optical counterparts to gravitational wave merger events.
science theme: Galaxies
schedule: Wed, 13:00 - 13:15 MDT |
video (youtube)
Joanne Hughes
Seattle University
The WLM dwarf irregular galaxy has been forming stars for at least 12 Gyr. Including APO data, we compiled a large FOV imaging survey in CBVRI filters in order to break the age-metallicity degeneracy of stars on the RGB by fitting color-pairs to spectroscopic data. The metallicity range is found to be −0.4 > [Fe/H] > −2.6 overall, where RGB stars with ages of 2-13 Gyr have a mean of [Fe/H]=−1.70 ± 0.01 dex, compared to [Fe/H]=-1.29 ± 0.01 dex for younger stars. We show that rapid chemical self-enrichment has only occurred within the last 2 Gyr for this isolated galaxy, independent of theoretical models.
science theme: Galaxies
schedule: Wed, 13:15 - 13:30 MDT |
video (youtube)
Mark Croom
New Mexico State University
Understanding galaxy evolution is a primary objective of extragalactic astronomy. Progress requires knowing the astrophysics of the circumgalactic medium (CGM), which is the key gas reservoir surrounding galaxies because this gas feeds star formation and has been dynamically mixed by outflowing gas from the interstellar medium and infalling gas from the intergalactic medium. The current favored hypothesis is that co-rotating accretion of metal-poor gas occurs near the disk plane, driving galaxy rotation and regulating star formation, while outflows eject metal-enriched gas to ∼200 kpc along the galactic poles. However, this "baryonic cycle” has been observed only for low-ionization gas traced by MgII absorption. High-ionization gas traced by OVI absorption shows no kinematic co-rotation and is a static “halo” disengaged from the low-ionization baryon cycle. A complete picture requires incorporating intermediate ionization gas (traced by CIV absorption). We have been undertaking an ambitious program using APO to obtain the rotation curves and star formation rates of ~40 edge-on spiral galaxies for which we have just been awarded Cycle 29 HST time to observe CIV absorption kinematics in their CGM. These observations will provide a more complete picture of the CGM baryon cycle and be used to constrain theoretical galaxy evolution scenarios.
science theme: Galaxies
schedule: Wed, 13:30 - 13:45 MDT |
video (youtube)
Dmitry Bizyaev
Apache Point Observatory
We present results of observations of more than 140 galaxies with high radial-to-vertical stellar disk scales ratio (also called superthin galaxies, or STGs). Spectral observations were conducted with the DIS spectrograph at APO, which allowed us to obtain the ionized gas rotation curves with R ~ 5000. Some galaxies have been observed with NICFPS for their NIR photometry. The spectra, the NIR photometry and published optical and NIR photometry were used for modeling that took into account the thickness of the stellar disk and rotation curves simultaneously. As a result, we measured masses and scale lengths of galactic dark halos. We notice systematic differences between the properties of our red and blue STGs: the blue STGs have a large fraction of dynamically under-evolved galaxies whose vertical velocity dispersion is low in both gas and stellar disks. The dark halo-to-disk scale ratio is shorter in the red STGs than in the blue ones, but in a majority of all STGs this ratio is under 2 (in conrast to larger values for regular galaxies). We investigate properties of STGs and possible evolutionary scenarios of their formation using our unique, large sample of these objects.
science theme: Galaxies
schedule: Wed, 13:45 - 14:00 MDT |
video (youtube)
Kelly Sanderson
New Mexico State University
Nebulous regions of ionized gas extending out to tens of pkpc from their host and partially into the circumgalactic medium are known as extended emission line regions (EELR). Studying EELR offers insight into the physical properties of the extended gas fueling galaxy growth, the radiative and kinetic energies escaping the host galaxies, the effects of galactic scale feedback, and the characteristic timescales over which this feedback occurs. Radio galaxy powered EELRs represent a particular phase in the evolution of active galaxies yet little is known about their evolution due to their rarity at intermediate redshifts. The goal of this research is to characterize the properties of radio galaxies with EELRs at 0.2 < z < 0.6 by studying the properties of their EELRs. To do this, we are using ground-based spectroscopy from APO’s Dual Imaging Spectrograph to characterize a sample of jetted radio galaxies hosting EELRs.
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