Mountains in the Deep

When Evan, prince of the Fourth Quadrant, sees a vision of a ghost-like crown hovering over his father\u27s head, he is sent on a dangerous mission to face the mystical shadow beast ravaging his kingdom--the same beast that has marked him as its prey and that will stop at nothing to hunt him down

Imaging Extended Emission-Line Regions of Obscured AGN with the Subaru Hyper Suprime-Cam Survey

Narrow-line regions excited by active galactic nuclei (AGN) are important for studying AGN photoionization and feedback. Their strong [O III] lines can be detected with broadband images, allowing morphological studies of these systems with large-area imaging surveys. We develop a new technique to reconstruct the [O III] images using the Subaru Hyper Suprime-Cam (HSC) Survey aided with spectra from the Sloan Digital Sky Survey (SDSS). The technique involves a careful subtraction of the galactic continuum to isolate emission from the [O III]$\lambda$5007 and [O III]$\lambda$4959 lines. Compared to traditional targeted observations, this technique is more efficient at covering larger samples with less dedicated observational resources. We apply this technique to an SDSS spectroscopically selected sample of 300 obscured AGN at redshifts 0.1 - 0.7, uncovering extended emission-line region candidates with sizes up to tens of kpc. With the largest sample of uniformly derived narrow-line region sizes, we revisit the narrow-line region size-luminosity relation. The area and radii of the [O III] emission-line regions are strongly correlated with the AGN luminosity inferred from the mid-infrared (15 $\mu$m rest-frame) with a power-law slope of $0.62^{+0.05}_{-0.06} \pm 0.10$ (statistical and systemic errors), consistent with previous spectroscopic findings. We discuss the implications for the physics of AGN emission-line region and future applications of this technique, which should be useful for current and next-generation imaging surveys to study AGN photoionization and feedback with large statistical samples.Comment: 20 pages, 13 figures, MNRAS submitte

Sumo Puff: Tidal Debris or Disturbed Ultra-Diffuse Galaxy?

We report the discovery of a diffuse stellar cloud with an angular extent $\gtrsim30^{\prime\prime}$, which we term "Sumo Puff", in data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). While we do not have a redshift for this object, it is in close angular proximity to a post-merger galaxy at redshift $z=0.0431$ and is projected within a few virial radii (assuming similar redshifts) of two other ${\sim}L_\star$ galaxies, which we use to bracket a potential redshift range of $0.0055 < z < 0.0431$. The object's light distribution is flat, as characterized by a low Sersic index ($n\sim0.3$). It has a low central $g$-band surface brightness of ${\sim}26.4$ mag arcsec$^{-2}$, large effective radius of ${\sim}13^{\prime\prime}$ (${\sim}11$ kpc at $z=0.0431$ and ${\sim}1.5$ kpc at $z=0.0055$), and an elongated morphology ($b/a\sim0.4$). Its red color ($g-i\sim1$) is consistent with a passively evolving stellar population and similar to the nearby post-merger galaxy, and we may see tidal material connecting Sumo Puff with this galaxy. We offer two possible interpretations for the nature of this object: (1) it is an extreme, galaxy-size tidal feature associated with a recent merger event, or (2) it is a foreground dwarf galaxy with properties consistent with a quenched, disturbed ultra-diffuse galaxy. We present a qualitative comparison with simulations that demonstrates the feasibility of forming a structure similar to this object in a merger event. Follow-up spectroscopy and/or deeper imaging to confirm the presence of the bridge of tidal material will be necessary to reveal the true nature of this object.Comment: 10 pages, 5 figures, submitted to PASJ for the HSC-SSP special issu

Discovery of a close-separation binary quasar at the heart of a z~0.2 merging galaxy and its implications for low-frequency gravitational waves

Supermassive black hole (SMBH) binaries with masses of ~10^8--10^9 Msun are expected to dominate the contribution to the as-yet undetected gravitational wave background (GWB) signal at the nanohertz frequencies accessible to Pulsar Timing Arrays (PTA). We currently lack firm empirical constraints on the amplitude of the GWB due to the dearth of confirmed SMBH binaries in the required mass range. Using HST/WFC3 images, we have discovered a z~0.2 quasar hosted in a merger remnant with two closely separated (0.13'' or ~430pc) continuum cores at the heart of the galaxy SDSSJ1010+1413. The two cores are spatially coincident with two powerful [OIII]-emitting point sources with quasar-like luminosities (L_AGN ~ 5x10^46 erg/s, suggesting the presence of a bound SMBH system, each with M_BH > 4x10^8 Msun. We place an upper limit on the merging timescale of the SMBH pair of 2.5 billion years, roughly the Universe lookback time at z~0.2. There is likely a population of quasar binaries similar to SDSSJ1010+1413 that contribute to a stochastic GWB that should be detected in the next several years. If the GWB is not detected this could indicate that SMBHs merge only over extremely long timescales, remaining as close separation binaries for many Hubble times, the so-called `final-parsec problem'.Comment: Accepted to ApJL (in press), 9 pages, 5 figure

The Inverse Redshift-Space Operator: Reconstructing Cosmological Density and Velocity Fields

We present the linear inverse redshift space operator which maps the galaxy density field derived from redshift surveys from redshift space to real space. Expressions are presented for observers in both the CMBR and Local Group rest frames. We show how these results can be generalised to flux--limited galaxy redshift surveys. These results allow the straightforward reconstruction of real space density and velocity fields without resort to iterative or numerically intensive inverse methods. As a corollary to the inversion of the density in the Local Group rest frame we present an expression for estimating the real space velocity dipole from redshift space, allowing one to estimate the Local Group dipole without full reconstruction of the redshift survey. We test these results on some simple models and find the reconstruction is very accurate. A new spherical harmonic representation of the redshift distortion and its inverse is developed, which simplifies the reconstruction and allows analytic calculation of the properties of the reconstructed redshift survey. We use this representation to analyse the uncertainties in the reconstruction of the density and velocity fields from redshift space, due to only a finite volume being available. Both sampling and shot-noise variance terms are derived and we discuss the limits of reconstruction analysis. We compare the reconstructed velocity field with the true velocity field and show that reconstruction in the Local Group rest frame is preferable, since this eliminates the major source of uncertainty from the dipole mode. These results can be used to transform redshift surveys to real space and may be used as part of a full likelihood analysis to extract cosmological parameters.Comment: 13 pages (Latex), 6 postscript figures included, accepted for publication in MNRA

Health care workers' need for headspace: findings from a multisite definitive randomized controlled trial of an unguided digital mindfulness-based self-help app to reduce Healthcare Worker Stress

Background: Health care workers experience high stress. Accessible, affordable, and effective approaches to reducing stress are lacking. In-person mindfulness-based interventions can reduce health care worker stress but are not widely available or accessible to busy health care workers. Unguided, digital, mindfulness-based self-help (MBSH) interventions show promise and can be flexibly engaged with. However, their effectiveness in reducing health care worker stress has not yet been explored in a definitive trial. Objective: This study aimed to investigate the effectiveness of an unguided digital MBSH app (Headspace) in reducing health care worker stress. Methods: This was a definitive superiority randomized controlled trial with 2182 National Health Service staff in England recruited on the web and allocated in a 1:1 ratio to fully automated Headspace (n=1095, 50.18%) or active control (Moodzone; n=1087, 49.82%) for 4.5 months. Outcomes were subscales of the Depression, Anxiety, and Stress (primary outcome) Scale short form; Short Warwick Edinburgh Mental Well-being Scale; Maslach Burnout Inventory; 15-item Five-Facet Mindfulness Questionnaire minus Observe items; Self-Compassion Scale-Short Form; Compassionate Love Scale; Penn State Worry Questionnaire; Brooding subscale of the Ruminative Response Scale; and sickness absence. Results: Intention-to-treat analyses found that Headspace led to greater reductions in stress over time than Moodzone (b=-0.31, 95% CI -0.47 to -0.14; P0; P=.65, .67, and .35), ruminative brooding (b=-0.06, 95% CI -0.12 to 0.00; P=.06), or sickness absence (γ=0.09, 95% CI -0.18 to 0.34). Per-protocol effects of Headspace (454/1095, 41.46%) versus Moodzone (283/1087, 26.03%) over time were found for stress, self-compassion, and compassion for others but not for the other outcomes. Engagement (practice days per week) and improvements in self-compassion during the initial 1.5-month intervention period mediated pre- to postintervention improvements in stress. Improvements in mindfulness, rumination, and worry did not mediate pre- to postintervention improvements in stress. No serious adverse events were reported. Conclusions: An unguided digital MBSH intervention (Headspace) can reduce health care workers' stress. Effect sizes were small but could have population-level benefits. Unguided digital MBSH interventions can be part of the solution to reducing health care worker stress alongside potentially costlier but potentially more effective in-person mindfulness-based interventions, nonmindfulness courses, and organizational-level interventions

A Study of Two Diffuse Dwarf Galaxies in the Field

We present optical long-slit spectroscopy and far-ultraviolet to near-infrared spectral energy distribution fitting of two diffuse dwarf galaxies, LSBG-285 and LSBG-750, which were recently discovered by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We measure redshifts using H$\alpha$ line emission, and find that these galaxies are at comoving distances of ${\approx}25$ and ${\approx}41$ Mpc, respectively, after correcting for the local velocity field. They have effective radii of $r_\mathrm{eff}=1.2$ and 1.8 kpc and stellar masses of $M_\star\approx2$-$3\times10^{7}~M_\odot$. There are no massive galaxies ($M_\star>10^{10} M_\odot$) within a comoving separation of at least 1.5 Mpc from LSBG-285 and 2 Mpc from LSBG-750. These sources are similar in size and surface brightness to ultra-diffuse galaxies, except they are isolated, star-forming objects that were optically selected in an environmentally blind survey. Both galaxies likely have low stellar metallicities $[Z_\star/Z_\odot] < -1.0$ and are consistent with the stellar mass-metallicity relation for dwarf galaxies. We set an upper limit on LSBG-750's rotational velocity of ${\sim}50$ km s$^{-1}$, which is comparable to dwarf galaxies of similar stellar mass with estimated halo masses $<10^{11}~M_\odot$. We find tentative evidence that the gas-phase metallicities in both of these diffuse systems are high for their stellar mass, though a statistically complete, optically-selected galaxy sample at very low surface brightness will be necessary to place these results into context with the higher-surface-brightness galaxy population.Comment: 16 pages, 6 figures; accepted for publication in Ap

Subaru Hyper Suprime-Cam View of Quasar Host Galaxies at z < 1

Active galactic nuclei (AGNs) are key for understanding the coevolution of galaxies and supermassive black holes (SMBHs). AGN activity is thought to affect the properties of their host galaxies, via a process called "AGN feedback", which drives the co-evolution. From a parent sample of 1151 z < 1 type-1 quasars from the Sloan Digital Sky Survey quasar catalog, we detected host galaxies of 862 of them in the high-quality grizy images of the Subaru Hyper Suprime-Cam (HSC) survey. The unprecedented combination of the survey area and depth allows us to perform a statistical analysis of the quasar host galaxies, with small sample variance. We fit the radial image profile of each quasar as a linear combination of the point spread function and the Sersic function, decomposing the images into the quasar nucleus and the host galaxy components. We found that the host galaxies are massive, with stellar mass Mstar > 10^(10) Msun, and are mainly located on the green valley. This trend is consistent with a scenario in which star formation of the host galaxies is suppressed by AGN feedback, that is, AGN activity may be responsible for the transition of these galaxies from the blue cloud to the red sequence. We also investigated the SMBH mass to stellar mass relation of the z < 1 quasars, and found a consistent slope with the local relation, while the SMBHs may be slightly undermassive. However, the above results are subject to our sample selection, which biases against host galaxies with low masses and/or large quasar-to-host flux ratios.Comment: Accepted for publication in PAS

Data work: how energy advisors and clients make IoT data accountable

We present fieldwork findings from the deployment of an interactive sensing system that supports the work of energy advisors who give face-to-face advice to low-income households in the UK. We focus on how the system and the data it produced are articulated in the interactions between professional energy advisors and their clients, and how they collaboratively anticipate, rehearse, and perform data work. In addition to documenting how the system was appropriated in advisory work, we elaborate the ‘overhead cost’ of building collaborative action into connected devices and sensing systems, and the commensurate need to support discrete workflows and accountability systems to enable the methodical incorporation of the IoT into collaborative action. We contribute an elaboration of the social, collaborative methods of data work relevant to those who seek to design and study collaborative IoT systems

Tidal Features at 0.05<z<0.45 in the Hyper Suprime-Cam Subaru Strategic Program: Properties and Formation Channels

We present 1,201 galaxies at $0.05<z<0.45$ that host tidal features, detected from the first $\sim\! 200$ deg$^2$ of imaging from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). All galaxies in the present sample have spectroscopic observations from the Sloan Digital Sky Survey (SDSS) spectroscopic campaigns, generating a sample of 21208 galaxies. Of these galaxies, we identify 214 shell systems and 987 stream systems. For 575 of these systems, we are additionally able to measure the $(g-i)$ colors of the tidal features. We find evidence for star formation in a subset of the streams, with the exception of streams around massive ellipticals, and find that stream host galaxies span the full range of stellar masses in our sample. Galaxies which host shells are predominantly red and massive: we find that observable shells form more frequently around ellipticals than around disc galaxies of the same stellar mass. Although the majority of the shells in our sample are consistent with being formed by minor mergers, $15\% \pm 4.4\%$ of shell host galaxies have $(g-i)$ colors as red as their host galaxy, consistent with being formed by major mergers. These "red shells" are additionally preferentially aligned with the major axis of the host galaxy, as previously predicted from simulations. We suggest that although the bulk of the observable shell population originates from fairly minor mergers, which preferentially form shells that are not aligned with the major axis of the galaxy, major mergers produce a significant number of observable shells.Comment: 24 pages, 14 figures. Submitted to Ap