arXiv subjects

Maren Cosens

Publications and source records attributed to Maren Cosens.

36 records · Page 2Linked to original sources

arXiv2022

Kinematics and Feedback in H II regions in the Dwarf Starburst Galaxy IC 10

We present a survey of the central region of the nearest starburst galaxy, IC 10, using the W. M. Keck Observatory Keck Cosmic Web Imager (KCWI) at high spectral and spatial resolution. We map the central starburst of IC 10 to sample the kinematic and ionization properties of the individual star-forming regions. Using the low spectral resolution mode of KCWI we map the oxygen abundance and with the high spectral resolution mode we identify 46 individual H II regions. These H II regions have an average radius of 4.0 pc, star formation rate $\sim1.3\times10^{-4}$ M$_\odot$ yr$^{-1}$, and velocity dispersion $\sim$16 km s$^{-1}$. None of the H II regions appear to be virialized ($\rm α_{vir}>>1$), and, on average, they show evidence of ongoing expansion. IC 10's H II regions are offset from the star forming region size-luminosity scaling relationships, as well as Larson's Law that relates size and velocity dispersion. We investigate the balance of inward and outward pressure, $\rm P_{in}$ and $\rm P_{out}$, finding $\rm P_{out}>P_{in}$ in 89% of H II regions, indicating feedback driven expansion even in these low mass H II regions. We find warm gas pressure ($\rm P_{gas}$) provides the dominant contribution to the outward pressure ($\rm P_{out}$). This counteracts the inward pressure which is dominated by turbulence in the surrounding gas rather than self-gravity. Five H II regions show evidence of outflows which are most likely supported by either stellar winds (2 regions) or champagne flows (3 regions). These observations provide new insights into the state of the star-forming regions in IC 10 and negative feedback from low mass clusters.

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arXiv2021

The Lick AGN Monitoring Project 2016: Velocity-Resolved Hβ Lags in Luminous Seyfert Galaxies

We carried out spectroscopic monitoring of 21 low-redshift Seyfert 1 galaxies using the Kast double spectrograph on the 3-m Shane telescope at Lick Observatory from April 2016 to May 2017. Targeting active galactic nuclei (AGN) with luminosities of λLλ (5100 Å) = 10^44 erg/s and predicted Hβ lags of 20-30 days or black hole masses of 10^7-10^8.5 Msun, our campaign probes luminosity-dependent trends in broad-line region (BLR) structure and dynamics as well as to improve calibrations for single-epoch estimates of quasar black hole masses. Here we present the first results from the campaign, including Hβ emission-line light curves, integrated Hβ lag times (8-30 days) measured against V-band continuum light curves, velocity-resolved reverberation lags, line widths of the broad Hβ components, and virial black hole mass estimates (10^7.1-10^8.1 Msun). Our results add significantly to the number of existing velocity-resolved lag measurements and reveal a diversity of BLR gas kinematics at moderately high AGN luminosities. AGN continuum luminosity appears not to be correlated with the type of kinematics that its BLR gas may exhibit. Follow-up direct modeling of this dataset will elucidate the detailed kinematics and provide robust dynamical black hole masses for several objects in this sample.

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arXiv2021

Panoramic SETI: overall mechanical system design

PANOSETI (Pulsed All-Sky Near-infrared Optical Search for Extra Terrestrial Intelligence) is a dedicated SETI (Search for Extraterrestrial Intelligence) observatory that is being designed to observe 4,441 sq. deg. to search for nano- to milli-second transient events. The experiment will have a dual observatory system that has a total of 90 identical optical 0.48 m telescopes that each have a 99 square degree field of view. The two observatory sites will be separated by 1 km distance to help eliminate false positives and register a definitive signal. We discuss the overall mechanical design of the telescope modules which includes a Fresnel lens housing, a shutter, three baffles, an 32x32 array of Hamamatsu Multi-Photon Pixel Counting (MPPC) detectors that reside on a linear stage for focusing. Each telescope module will be housed in a triangle of a 3rd tessellation frequency geodesic dome that has the ability to have directional adjustment to correct for manufacturing tolerances and astrometric alignment to the second observatory site. Each observatory will have an enclosure to protect the experiment, and an observatory room for operations and electronics. We will review the overall design of the geodesic domes and mechanical telescope attachments, as well as the overall cabling and observatory infrastructure layout.

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arXiv2021

A Spatially-Resolved Survey of Distant Quasar Host Galaxies: I. Dynamics of galactic outflows

We present observations of ionized gas outflows in eleven z$ =1.39-2.59$ radio-loud quasar host galaxies. Data was taken with the integral field spectrograph (IFS) OSIRIS and the adaptive optics system at the W.M. Keck Observatory targeting nebular emission lines (H$β$, [OIII], H$α$, [NII] and [SII]) redshifted into the near-infrared (1-2.4 \micron). Outflows with velocities of 500 - 1700 km\,s$^{-1}$ are detected in 10 systems on scales ranging from $<1$ kpc to 10 kpc with outflow rates from 8-2400 M$_\odot$yr$^{-1}$. For five sources, the outflow momentum rates are 4-80 times $L_{AGN}$/c, consistent with outflows being driven by an energy conserving shock. The five other outflows are either driven by radiation pressure or an isothermal shock. The outflows are the dominant source of gas depletion, and we find no evidence for star formation along the outflow paths. For eight objects, the outflow paths are consistent with the orientation of the jets. Yet, given the calculated pressures, we find no evidence of the jets currently doing work on these galactic-scale ionized outflows. We find that galactic-scale feedback occurs well before galaxies establish a substantial fraction of their stellar mass, as expected from local scaling relationships.

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arXiv2021

Powerful winds in high-redshift obscured and red quasars

Quasar-driven outflows must have made their most significant impact on galaxy formation during the epoch when massive galaxies were forming most rapidly. To study the impact of quasar feedback we conducted rest-frame optical integral field spectrograph (IFS) observations of three extremely red quasars (ERQs) and one type-2 quasar at $z=2-3$, obtained with the NIFS and OSIRIS instruments at the Gemini North and W. M. Keck Observatory with the assistance of laser-guided adaptive optics. We use the kinematics and morphologies of the [OIII] 5007Åand H$α$ 6563Åemission lines redshifted into the near-infrared to gauge the extents, kinetic energies and momentum fluxes of the ionized outflows in the quasars host galaxies. For the ERQs, the galactic-scale outflows are likely driven by radiation pressure in a high column density environment or due to an adiabatic shock. For the type-2 quasar, the outflow is driven by radiation pressure in a low column density environment or due to a radiative shock. The outflows in the ERQs carry a significant amount of energy ranging from 0.05-5$\%$ of the quasar's bolometric luminosity, powerful enough to have a significant impact on the quasar host galaxies. However, the outflows are likely only impacting the inner few kpc of each host galaxy. The observed outflow sizes are generally smaller than other ionized outflows observed at high redshift. The high ratio between the momentum flux of the ionized outflow and the photon momentum flux from the quasar accretion disk and high nuclear obscuration makes these ERQs great candidates for transitional objects where the outflows are likely responsible for clearing material in the inner regions of each galaxy, unveiling the quasar accretion disk at optical wavelengths.

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arXiv2021

Liger for Next Generation Keck AO: Filter Wheel and Pupil Design

Liger is a next-generation near-infrared imager and integral field spectrograph (IFS) for the W.M. Keck Observatory designed to take advantage of the Keck All-Sky Precision Adaptive Optics (KAPA) upgrade. Liger will operate at spectral resolving powers between R$\sim$4,000 - 10,000 over a wavelength range of 0.8-2.4$μ$m. Liger takes advantage of a sequential imager and spectrograph design that allows for simultaneous observations between the two channels using the same filter wheel and cold pupil stop. We present the design for the filter wheels and pupil mask and their location and tolerances in the optical design. The filter mechanism is a multi-wheel design drawing from the heritage of the current Keck/OSIRIS imager single wheel design. The Liger multi-wheel configuration is designed to allow future upgrades to the number and range of filters throughout the life of the instrument. The pupil mechanism is designed to be similarly upgradeable with the option to add multiple pupil mask options. A smaller wheel mechanism allows the user to select the desired pupil mask with open slots being designed in for future upgrade capabilities. An ideal pupil would match the shape of the image formed of the primary and would track its rotation. For different pupil shapes without tracking we model the additional exposure time needed to achieve the same signal to noise of an ideal pupil and determine that a set of fixed masks of different shapes provides a mechanically simpler system with little compromise in performance.

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arXiv2021

Liger for Next Generation Keck Adaptive Optics: Opto-Mechanical Dewar for Imaging Camera and Slicer

Liger is a next generation adaptive optics (AO) fed integral field spectrograph (IFS) and imager for the W. M. Keck Observatory. This new instrument is being designed to take advantage of the upgraded AO system provided by Keck All-Sky Precision Adaptive-optics (KAPA). Liger will provide higher spectral resolving power (R$\sim$4,000-10,000), wider wavelength coverage ($\sim$0.8-2.4 $μ$m), and larger fields of view than any current IFS. We present the design and analysis for a custom-made dewar chamber for characterizing the Liger opto-mechanical system. This dewar chamber is designed to test and assemble the Liger imaging camera and slicer IFS components while being adaptable for future experiments. The vacuum chamber will operate below $10^{-5}$ Torr with a cold shield that will be kept below 90 K. The dewar test chamber will be mounted to an optical vibration isolation platform and further isolated from the cryogenic and vacuum systems with bellows. The cold head and vacuums will be mounted to a custom cart that will also house the electronics and computer that interface with the experiment. This test chamber will provide an efficient means of calibrating and characterizing the Liger instrument and performing future experiments.

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arXiv2021

A Spatially-Resolved Survey of Distant Quasar Host Galaxies: II. Photoionization and Kinematics of the ISM

We present detailed observations of photoionization conditions and galaxy kinematics in eleven z$=1.39-2.59$ radio-loud quasar host galaxies. Data was taken with OSIRIS integral field spectrograph (IFS) and the adaptive optics system at the W.M. Keck Observatory that targeted nebular emission lines (H$β$,[OIII],H$α$,[NII]) redshifted into the near-infrared (1-2.4 \micron). We detect extended ionized emission on scales ranging from 1-30 kpc photoionized by stars, shocks, and active galactic nuclei (AGN). Spatially resolved emission-line ratios indicate that our systems reside off the star formation and AGN-mixing sequence on the Baldwin, Phillips $\&$ Terlevich (BPT) diagram at low redshift. The dominant cause of the difference between line ratios of low redshift galaxies and our sample is due to lower gas-phase metallicities, which are 2-5$\times$ less compared to galaxies with AGN in the nearby Universe. Using gas velocity dispersion as a proxy to stellar velocity dispersion and dynamical mass measurement through inclined disk modeling we find that the quasar host galaxies are under-massive relative to their central supermassive black hole (SMBH) mass, with all systems residing off the local scaling ($M_{\bullet}-σ~$,$M_{\bullet}-M_{*}~$) relationship. These quasar host galaxies require substantial growth, up to an order of magnitude in stellar mass, to grow into present-day massive elliptical galaxies. Combining these results with part I of our sample paper (Vayner et al. 2021) we find evidence for winds capable of causing feedback before the AGN host galaxies land on the local scaling relation between black hole and galaxy stellar mass, and before the enrichment of the ISM to a level observed in local galaxies with AGN.

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arXiv2019

Detector Characterization of a Near-Infrared Discrete Avalanche Photodiode 5x5 Array for Astrophysical Observations

We present detector characterization of a state-of-the-art near-infrared (950nm - 1650 nm) Discrete Avalanche Photodiode detector (NIRDAPD) 5x5 array. We designed an experimental setup to characterize the NIRDAPD dark count rate, photon detection efficiency (PDE), and non-linearity. The NIRDAPD array was illuminated using a 1050 nm light-emitting diode (LED) as well as 980 nm, 1310 nm, and 1550 nm laser diodes. We find a dark count rate of 3.3x10$^6$ cps, saturation at 1.2x10$^8$ photons per second, a photon detection efficiency of 14.8% at 1050 nm, and pulse detection at 1 GHz. We characterized this NIRDAPD array for a future astrophysical program that will search for technosignatures and other fast (>1 Ghz) astrophysical transients as part of the Pulsed All-sky Near-infrared Optical Search for Extraterrestrial Intelligence (PANOSETI) project. The PANOSETI program will consist of an all-sky optical (350 - 800 nm) observatory capable of observing the entire northern hemisphere instantaneously and a wide-field NIR (950 - 1650 nm) component capable of drift scanning the entire sky in 230 clear nights. PANOSETI aims to be the first wide-field fast-time response near-infrared transient search.

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arXiv2018

Characterizing and Improving the Data Reduction Pipeline for the Keck OSIRIS Integral Field Spectrograph

OSIRIS is a near-infrared (1.0--2.4 $μ$m) integral field spectrograph operating behind the adaptive optics system at Keck Observatory, and is one of the first lenslet-based integral field spectrographs. Since its commissioning in 2005, it has been a productive instrument, producing nearly half the laser guide star adaptive optics (LGS AO) papers on Keck. The complexity of its raw data format necessitated a custom data reduction pipeline (DRP) delivered with the instrument in order to iteratively assign flux in overlapping spectra to the proper spatial and spectral locations in a data cube. Other than bug fixes and updates required for hardware upgrades, the bulk of the DRP has not been updated since initial instrument commissioning. We report on the first major comprehensive characterization of the DRP using on-sky and calibration data. We also detail improvements to the DRP including characterization of the flux assignment algorithm; exploration of spatial rippling in the reduced data cubes; and improvements to several calibration files, including the rectification matrix, the bad pixel mask, and the wavelength solution. We present lessons learned from over a decade of OSIRIS data reduction that are relevant to the next generation of integral field spectrograph hardware and data reduction software design.

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arXiv2018

Size-Luminosity Scaling Relations of Local and Distant Star Forming Regions

We investigate star forming scaling relations using Bayesian inference on a comprehensive data sample of low- (z<0.1) and high-redshift (1<z<5) star forming regions. This full data set spans a wide range of host galaxy stellar mass ($M_{*} \sim10^6-10^{11} M_{\odot}$) and clump star formation rates (SFR $ \sim10^{-5}-10^2 M_\odot yr^{-1}$). We fit the power-law relationship between the size (r$_{Hα}$) and luminosity (L$_{Hα}$) of the star forming clumps using the Bayesian statistical modeling tool Stan that makes use of Markov Chain Monte Carlo (MCMC) sampling techniques. Trends in the scaling relationship are explored for the full sample and subsets based on redshift and selection effects between samples. In our investigation we find no evidence of redshift evolution of the size-luminosity scaling relationship, nor a difference in slope between lensed and unlensed data. There is evidence of a break in the scaling relationship between high and low star formation rate surface density ($Σ_{SFR}$) clumps. The size-luminosity power law fit results are L$_{Hα}\sim$ r$_{Hα}^{2.8}$ and L$_{Hα}\sim$ r$_{Hα}^{1.7}$ for low and high $Σ_{SFR}$ clumps, respectively. We present a model where star forming clumps form at locations of gravitational instability and produce an ionized region represented by the Strömgren radius. A radius smaller than the scale height of the disk results in a scaling relationship of $L \propto r^3$ (high $Σ_{SFR}$ clumps), and a scaling of $L \propto r^2$ (low $Σ_{SFR}$ clumps) if the radius is larger than the disk scale height.

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arXiv2018

Panoramic optical and near-infrared SETI instrument: prototype design and testing

The Pulsed All-sky Near-infrared Optical Search for ExtraTerrestrial Intelligence (PANOSETI) is an instrument program that aims to search for fast transient signals (nano-second to seconds) of artificial or astrophysical origin. The PANOSETI instrument objective is to sample the entire observable sky during all observable time at optical and near-infrared wavelengths over 300 - 1650 nm$^1$. The PANOSETI instrument is designed with a number of modular telescope units using Fresnel lenses ($\sim$0.5m) arranged on two geodesic domes in order to maximize sky coverage$^2$. We present the prototype design and tests of these modular Fresnel telescope units. This consists of the design of mechanical components such as the lens mounting and module frame. One of the most important goals of the modules is to maintain the characteristics of the Fresnel lens under a variety of operating conditions. We discuss how we account for a range of operating temperatures, humidity, and module orientations in our design in order to minimize undesirable changes to our focal length or angular resolution.

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arXiv2018

Panoramic optical and near-infrared SETI instrument: overall specifications and science program

We present overall specifications and science goals for a new optical and near-infrared (350 - 1650 nm) instrument designed to greatly enlarge the current Search for Extraterrestrial Intelligence (SETI) phase space. The Pulsed All-sky Near-infrared Optical SETI (PANOSETI) observatory will be a dedicated SETI facility that aims to increase sky area searched, wavelengths covered, number of stellar systems observed, and duration of time monitored. This observatory will offer an "all-observable-sky" optical and wide-field near-infrared pulsed technosignature and astrophysical transient search that is capable of surveying the entire northern hemisphere. The final implemented experiment will search for transient pulsed signals occurring between nanosecond to second time scales. The optical component will cover a solid angle 2.5 million times larger than current SETI targeted searches, while also increasing dwell time per source by a factor of 10,000. The PANOSETI instrument will be the first near-infrared wide-field SETI program ever conducted. The rapid technological advance of fast-response optical and near-infrared detector arrays (i.e., Multi-Pixel Photon Counting; MPPC) make this program now feasible. The PANOSETI instrument design uses innovative domes that house 100 Fresnel lenses, which will search concurrently over 8,000 square degrees for transient signals (see Maire et al. and Cosens et al., this conference). In this paper, we describe the overall instrumental specifications and science objectives for PANOSETI.

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arXiv2018

Panoramic optical and near-infrared SETI instrument: optical and structural design concepts

We propose a novel instrument design to greatly expand the current optical and near-infrared SETI search parameter space by monitoring the entire observable sky during all observable time. This instrument is aimed to search for technosignatures by means of detecting nano- to micro-second light pulses that could have been emitted, for instance, for the purpose of interstellar communications or energy transfer. We present an instrument conceptual design based upon an assembly of 198 refracting 0.5-m telescopes tessellating two geodesic domes. This design produces a regular layout of hexagonal collecting apertures that optimizes the instrument footprint, aperture diameter, instrument sensitivity and total field-of-view coverage. We also present the optical performance of some Fresnel lenses envisaged to develop a dedicated panoramic SETI (PANOSETI) observatory that will dramatically increase sky-area searched (pi steradians per dome), wavelength range covered, number of stellar systems observed, interstellar space examined and duration of time monitored with respect to previous optical and near-infrared technosignature finders.

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arXiv2018

Studying the [OIII]$λ$5007A emission-line width in a sample of $\sim$80 local active galaxies: A surrogate for $σ_{\star}$?

For a sample of $\sim$80 local ($0.02 \leq z \leq 0.1$) Seyfert-1 galaxies with high-quality long-slit Keck spectra and spatially-resolved stellar-velocity dispersion ($σ_{\star}$) measurements, we study the profile of the [OIII]$λ$5007A emission line to test the validity of using its width as a surrogate for $σ_{\star}$. Such an approach has often been used in the literature, since it is difficult to measure $σ_{\star}$ for type-1 active galactic nuclei (AGNs) due to the AGN continuum outshining the stellar-absorption lines. Fitting the [OIII] line with a single Gaussian or Gauss-Hermite polynomials overestimates $σ_{\star}$ by 50-100%. When line asymmetries from non-gravitational gas motion are excluded in a double Gaussian fit, the average ratio between the core [OIII] width ($σ_{\rm {[OIII],D}}$) and $σ_{\star}$ is $\sim$1, but with individual data points off by up to a factor of two. The resulting black-hole-mass-$σ_{\rm {[OIII],D}}$ relation scatters around that of quiescent galaxies and reverberation-mapped AGNs. However, a direct comparison between $σ_{\star}$ and $σ_{\rm {[OIII],D}}$ shows no close correlation, only that both quantities have the same range, average and standard deviation, probably because they feel the same gravitational potential. The large scatter is likely due to the fact that line profiles are a luminosity-weighted average, dependent on the light distribution and underlying kinematic field. Within the range probed by our sample (80-260 km s$^{-1}$), our results strongly caution against the use of [OIII] width as a surrogate for $σ_{\star}$ on an individual basis. Even though our sample consists of radio-quiet AGNs, FIRST radio-detected objects have, on average, a $\sim$10% larger [OIII] core width.

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arXiv2016

Discovery and Follow-up Observations of the Young Type Ia Supernova 2016coj

The Type~Ia supernova (SN~Ia) 2016coj in NGC 4125 (redshift $z=0.004523$) was discovered by the Lick Observatory Supernova Search 4.9 days after the fitted first-light time (FFLT; 11.1 days before $B$-band maximum). Our first detection (pre-discovery) is merely $0.6\pm0.5$ day after the FFLT, making SN 2016coj one of the earliest known detections of a SN Ia. A spectrum was taken only 3.7 hr after discovery (5.0 days after the FFLT) and classified as a normal SN Ia. We performed high-quality photometry, low- and high-resolution spectroscopy, and spectropolarimetry, finding that SN 2016coj is a spectroscopically normal SN Ia, but with a high velocity of \ion{Si}{2} $λ$6355 ($\sim 12,600$\,\kms\ around peak brightness). The \ion{Si}{2} $λ$6355 velocity evolution can be well fit by a broken-power-law function for up to a month after the FFLT. SN 2016coj has a normal peak luminosity ($M_B \approx -18.9 \pm 0.2$ mag), and it reaches a $B$-band maximum \about16.0~d after the FFLT. We estimate there to be low host-galaxy extinction based on the absence of Na~I~D absorption lines in our low- and high-resolution spectra. The spectropolarimetric data exhibit weak polarization in the continuum, but the \ion{Si}{2} line polarization is quite strong ($\sim 0.9\% \pm 0.1\%$) at peak brightness.

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arXiv2016

Broad Hbeta Emission-Line Variability in a Sample of 102 Local Active Galaxies

A sample of 102 local (0.02 < z < 0.1) Seyfert galaxies with black hole masses MBH > 10^7 M_sun was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10-m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hbeta emission line within the ~3-9 year time-frame between the two sets of spectra. The variability of the broad Hbeta emission line is of particular interest, not only since it is used to estimate MBH, but also since its strength and width is used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (~66%) of the objects, resulting in a Seyfert-type change for ~38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hbeta line virtually disappears in 3/102 (~3%) extreme cases. We discuss potential causes for these changing-look AGNs. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of H$β$ line variability in a sample of low-redshift Seyfert galaxies.

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arXiv2015

A Local Baseline of the Black Hole Mass Scaling Relations for Active Galaxies. III. The BH mass - $σ$ relation

We create a baseline of the black hole (BH) mass (MBH) - stellar-velocity dispersion (sigma) relation for active galaxies, using a sample of 66 local (0.02<z<0.09) Seyfert-1 galaxies, selected from the Sloan Digital Sky Survey (SDSS). Analysis of SDSS images yields AGN luminosities free of host-galaxy contamination and morphological classification. 51/66 galaxies have spiral morphology. 28 bulges have Sersic index n<2 and are considered candidate pseudo bulges, with eight being definite pseudo bulges based on multiple classification criteria met. Only 4/66 galaxies show sign of interaction/merging. High signal-to-noise ratio Keck spectra provide the width of the broad Hbeta emission line free of FeII emission and stellar absorption. AGN luminosity and Hbeta line widths are used to estimate MBH. The Keck-based spatially-resolved kinematics is used to determine stellar-velocity dispersion within the spheroid effective radius. We find that sigma can vary on average by up to 40% across definitions commonly used in the literature, emphasizing the importance of using self-consistent definitions in comparisons and evolutionary studies. The MBH-sigma relation for our Seyfert-1 galaxies has the same intercept and scatter as that of reverberation-mapped AGNs as well as quiescent galaxies, consistent with the hypothesis that our single epoch MBH estimator and sample selection do not introduce significant biases. Barred galaxies, merging galaxies, and those hosting pseudo bulges do not represent outliers in the MBH-sigma relation. This is in contrast with previous work, although no firm conclusion can be drawn due to the small sample size and limited resolution of the SDSS images.

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