Ohio University Lancaster

ABSTRACT We demonstrate the potential of Euclid ’s slitless spectroscopy to discover high-redshift ($z>5$) quasars and their main photometric contaminant, ultracool dwarfs. Sensitive infrared spectroscopy from space is able to efficiently identify both populations, as demonstrated by Euclid Near-Infrared Spectrometer and Photometer Red Grism (NISP ${\rm RG}_{\scriptscriptstyle \rm E}$) spectra of the newly discovered $z=5.404$ quasar EUCL J181530.01$+$652054.0, as well as several ultracool dwarfs in the Euclid Deep Field North and the Euclid Early Release Observation field Abell 2764. The ultracool dwarfs were identified by cross-correlating their spectra with templates. The quasar was identified by its strong and broad ${\rm C \small {III]}}$ and ${\rm Mg {\small II}}$ emission lines in the NISP ${\rm RG}_{\scriptscriptstyle \rm E}$ 1206–1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP ${\rm BG}_{\scriptscriptstyle \rm E}$) 926–1366 nm spectrum confirms ${C {\small IV}}$ and $\rm{C \small {III]}}$ emission. NISP ${\rm RG}_{\scriptscriptstyle \rm E}$ can find bright quasars at $z\approx 5.5$ and $z\gtrsim 7$, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01$+$652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array ($L_{\rm 144}=4.0 \times 10^{25}\,$W Hz$^{-1}$). The quasar has a bolometric luminosity of $3\times 10^{12}\, {{\rm L}_{\odot }}{}$ and is powered by a $3.4\times 10^9\, {{\rm M}_{\odot }}$ black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the $\approx$20 deg$^2$ surveyed. This finding highlights the potential and effectiveness of NISP spectroscopy in identifying rare, luminous high-redshift quasars, previewing the census of these sources that Euclid’s slitless spectroscopy will deliver over about $14\, 000\,$deg$^2$ of the sky.

We report on the terahertz (THz) harmonic generation in an active graphene/metamaterial device by using powerful ultrafast table-top THz time-domain spectroscopic systems. Complex nonlinear transmission spectra, comprising even and odd harmonics, emerge when the devices are tested with intense ultrafast THz pulses with peak electric fields in the range of 1–150 kV/cm. The odd and even harmonic features show a positive correlation with carrier concentration, allowing for efficient frequency tuning on top of tunable group delay dispersion. Interestingly, before the onset of saturation, observed at 20–25 kV/cm, the main resonance and the harmonic features exhibit an anti-crossing trend that can be further exploited for active frequency tuning. These results report a key milestone for the fundamental investigation of the nonlinearity of 2D materials. At the same time, they represent an important advance in the design of future integrated THz optoelectronics by providing novel functionalities for THz light generation and manipulation.

ABSTRACT Galaxy interaction and merging have clear effects on the systems involved. We find an increase in the star formation rate (SFR), potential ignition of active galactic nuclei (AGNs), and significant morphology changes. However, at what stage during interactions or mergers these changes begin to occur remains an open question. With a combination of machine learning and visual classification, we select a sample of 3162 interacting and merging galaxies in the Cosmic Evolutionary Survey (COSMOS) field across a redshift range of 0.0–1.2. We divide this sample into four distinct stages of interaction based on their morphology, each stage representing a different phase of the dynamical time-scale. We use the rich ancillary data available in COSMOS to probe the relation between interaction stage, stellar mass, SFR, and AGN fraction. We find that the distribution of SFRs rapidly changes with stage for mass distributions consistent with being drawn from the same parent sample. This is driven by a decrease in the fraction of red sequence galaxies (from 17 per cent as close pairs to 1.4 per cent during merging) and an increase in the fraction of starburst galaxies (from 7 per cent to 32 per cent). We find that the AGN fraction increases by a factor of 1.2 only at coalescence. We find that the effects of interaction peak at the point of closest approach and coalescence of the two systems. We show that the point in time of the underlying dynamical time-scale – and its related morphology – is as important to consider as its projected separation.

ABSTRACT Pulse profile modelling is a relativistic ray-tracing technique that can be used to infer masses, radii, and geometric parameters of neutron stars. In a previous study, we looked at the performance of this technique when applied to thermonuclear burst oscillations from accreting neutron stars. That study showed that ignoring the variability associated with burst oscillation sources resulted in significant biases in the inferred mass and radius, particularly for the high count rates that are nominally required to obtain meaningful constraints. In this follow-on study, we show that the bias can be mitigated by slicing the bursts into shorter segments where variability can be neglected, and jointly fitting the segments. Using this approach, the systematic uncertainties on the mass and radius are brought within the range of the statistical uncertainty. With about 106 source counts, this yields uncertainties of approximately 10 per cent for both the mass and radius. However, this modelling strategy requires substantial computational resources. We also confirm that the posterior distributions of the mass and radius obtained from multiple bursts of the same source can be merged to produce outcomes comparable to that of a single burst with an equivalent total number of counts.

One major outcome of the Federal Reserve's 2019 -20 framework review was the adoption of a Flexible Average Inflation Targeting (FAIT) strategy in August 2020. Using synthetic control methods, we document that U.S. inflation rose post-FAIT considerably more than predicted had the strategy not changed (an average of 1.18 percentage points during 2020:M8-2022:M2). To explore the extent to which targeting average inflation delayed the Fed's response and contributed to post-FAIT inflation, we adopt a version of the open-economy New Keynesian model in Martnez-Garca (2021) and document the economic consequences of adopting alternative measures of average inflation as policy objectives. We document three additional major findings using this general equilibrium setup: First, depending on how far back and how much weight is assigned to past inflation misses, the policy outcomes under FAIT are similar to those under the pre-FAIT regime. Secondly, we find that the implementation of FAIT can have large effects over short periods of time as it tends to delay action. However, over longer periods of time-such as the 1984:Q1-2019:Q4 pre-FAIT period-its effects wash out and appear negligible. Finally, we find that different average inflation measures explain an average of 0.5 percentage points per quarter of the post-FAIT inflation surge, indicating that targeting average inflation by itself can only explain part of the inflation spike since August 2020.

Melanoma, an extremely drug resistant form of cancer, displays elevated levels of growth hormone (GH) and growth hormone receptor (GHR) expression. We have described a GH dependent mechanism of chemoresistance in melanoma through a series of earlier studies. In GHR overexpressing human melanoma, GH action drives active drug efflux and phenotype switching by upregulating ATP-binding cassette transporters (ABC-transporters) and epithelial-to-mesenchymal transition (EMT) markers. Inhibition of GHR activation reverses these effects, increases drug retention, and sensitizes the melanoma cells to chemotherapy. GH action in melanoma also appears to drive drug sequestration in melanosomes as we present here. GH action was found to modulate the levels of melanocyte-inducing transcription factor (MITF), the master regulator of melanosome synthesis and melanoma. Additionally, MITF target gene levels and drug sequestering ABC transporter expression were also elevated by GH treatment in vitro and in vivo in mouse tumor xenografts. This was corroborated by in silico analyses of tumor databases. Furthermore, we observed a dose dependent increase in tyrosinase activity and melanogenesis in human melanoma cells with GH, in the presence of chemotherapy, which was suppressed by siRNA mediated GHR inhibition. Thus, we describe an array of molecular mechanisms by which GH drives chemoresistance in melanoma. Therefore, GHR inhibition combined with chemotherapy should lead to better tumor clearance and improve overall survival.