Sara Petty

Luminous infrared (IR) galaxies are key sites of obscured stellar mass assembly at z > 0.5. Their star formation rates (SFRs) are often estimated using the luminosities of the 6.2 and 11.2 μ m polycyclic aromatic hydrocarbon (PAH) features or those of the [Ne ii ] and [Ne iii ] fine-structure lines, as they are minimally affected by obscuration. It is uncertain whether the calibration of these features as SFR tracers depends on the starburst bolometric luminosity or the level of active galactic nucleus (AGN) activity. We here investigate the relationship between the luminosities of PAH and neon lines with SFR for highly luminous objects using radiative transfer modeling and archival observations of 42 local ultraluminous (≥10 ¹² L _⊙ ) IR galaxies (ULIRGs). We find that PAH and [Ne ii ] features arise mainly in star-forming regions, with small contributions from the AGN or host, but that the [Ne iii ] line has a mixed contribution from both star formation and AGN activity. We present relations between L _PAH and L _{[Ne II ]} , and both starburst luminosity and SFR. We find relations for lower-luminosity ( L _IR ≃ 10 ¹⁰ –10 ¹² L _⊙ ) systems underestimate the SFRs in local ULIRGs by up to ∼1 dex. The 6.2 and 11.2 μ m PAH features, and the [Ne ii ] line, are thus good tracers of SFR in ULIRGs. We do not find that a more luminous AGN affects the relationship between SFR and PAH or neon luminosity but that it can make PAH emission harder to discern. Our results and derived relations are relevant to studies of star-forming and composite galaxies at z < 3 with the James Webb Space Telescope.

A demonstrated failure mode for operational solar flare forecasting is the inability to forecast flares that occur near, or just beyond, the solar limb. To address this shortcoming, we develop a “” full‐heliosphere event forecasting framework and evaluate its statistical classification ability against this specific challenge. A magnetic surface flux transport model is used to generate full‐sun maps of the photospheric radial magnetic field from which active regions (ARs) are identified and tracked using a new labeling scheme that is observer‐location agnostic and allows for post‐facto modifications. Flare‐relevant magnetic parameters couple to a “visibility” index that specifies AR location relative to the visible solar limb and expected flare detection. Flare labels are assigned according to peak Soft X‐ray flux, and a statistical classification is performed using nonparametric discriminant analysis. A version where new or emerging ARs on the far (“invisible”) side of the Sun are incorporated into the model by way of far‐side helioseismology, is also tested. We evaluate the new framework by its performance specifically including the limb areas using Brier Skill Score and ROC Skill Score, finding improvement at the level or less. However, we do find that the number of False Negatives, or “missed” forecasts decreases, and find strong evidence that the additional information provided by the far‐side helioseismology can help predict near‐ and just‐beyond‐limb flares, particularly for East‐limb events. While individual components of this framework could be improved, we demonstrate that a known failure mode for solar flare forecasting can be mitigated with available resources.

Infrared-luminous galaxies are important sites of stellar and black hole mass assembly at most redshifts. Their luminosities are often estimated by fitting spectral energy distribution (SED) models to near- to far-infrared data, but the dependence of these estimates on the data used is not well understood. Here, using observations simulated from a well-studied local sample, we compare the effects of wavelength coverage, signal-to-noise ratio, flux calibration, angular resolution, and redshift on the recovery of starburst, active galactic nucleus (AGN), and host luminosities. We show that the most important factors are wavelength coverage that spans the peak in a SED, and dense wavelength sampling. Such observations recover starburst and AGN infrared luminosities with systematic bias below 20%. Starburst luminosities are best recovered with far-infrared observations, while AGN luminosities are best recovered with near- and mid-infrared observations, though the recovery of both are enhanced with near/mid-infrared and far-infrared observations, respectively. Host luminosities are best recovered with near/far-infrared observations, but are usually biased low, by ≳20%. The recovery of starburst and AGN luminosity is enhanced by observing at high angular resolution. Starburst-dominated systems show more biased recovery of luminosities than do AGN-dominated systems. As redshift increases, far-infrared observations become more capable and mid-infrared observations less capable at recovering luminosities. Our results highlight the transformative power of a far-infrared instrument with dense wavelength coverage, from tens to hundreds of microns, for studying infrared-luminous galaxies. We tabulate estimates of systematic bias and random error for use with JWST and other observatories.

Luminous infrared galaxies are key sites of obscured stellar mass assembly at z > 0.5. Their star formation rates (SFRs) are often estimated using the luminosities of the 6.2 micron and 11.2 micron polycyclic aromatic hydrocarbon (PAH) features, or those of the [Ne II] and [Ne III] fine-structure lines, as they are minimally affected by obscuration. It is uncertain whether the calibration of these features as SFR tracers depends on the starburst bolometric luminosity or the level of Active Galactic Nucleus (AGN) activity. We here investigate the relationship between the luminosities of PAH and Neon lines with star formation rate for highly luminous objects using radiative transfer modeling and archival observations of 42 local Ultraluminous (>= 10^12 L_sun) Infrared Galaxies (ULIRGs). We find that PAH and [Ne II] features arise mainly in star-forming regions, with small contributions from the AGN or host, but that the [Ne III] line has a mixed contribution from both star formation and AGN activity. We present relations between L_PAH and L_NeII, and both starburst luminosity and SFR. We find relations for lower luminosity (L_IR ~= 10^10-10^12 L_sun) systems underestimate the SFRs in local ULIRGs by up to ~1 dex. The 6.2 micron and 11.2 micron PAH features, and the [Ne II] line, are thus good tracers of SFR in ULIRGs. We do not find that a more luminous AGN affects the relationship between SFR and PAH or Neon luminosity, but that it can make PAH emission harder to discern. Our results and derived relations are relevant to studies of star-forming and composite galaxies at z < 3 with the James Webb Space Telescope.

The assembly of supermassive black hole (SMBH) mass (M _•) and stellar mass (M _*) in galaxies can be studied via the redshift evolution of the M _•–M _* relation, but the ways in which selection bias and physical assembly channels affect this evolution are uncertain. To address this, we compare the M _•–M _* relation for local massive (M _* > 10^10.5 M _⊙) quiescent early-type galaxies (ETGs) to that for massive ETGs hosting active galactic nuclei (AGN) at z ∼ 0.8. The restrictions on stellar mass and galaxy type limit the assembly channels that may connect the two relations. For the local sample we find log ( M • ) = 8.80 + 1.10 ( log M * − 11 ) , in line with prior work. For the z ∼ 0.8 sample we find a bias-corrected relation: log ( M • ) = 7.80 + 1.25 ( log M * − 11 ) . We show, however, that this relation depends on the stellar and SMBH mass functions used to compute the selection bias, the virial relation, the virial factor, and the active fraction, which together introduce uncertainty of up to ​​​​​​∼0.6 dex in the z ∼ 0.8 relation. Adopting reasonable choices of these parameters then our z ∼ 0.8 relation lies above that for z ∼ 0 AGN by ∼0.5 dex, but below our z ∼ 0 ETG relation by 0.4–1 dex in SMBH mass. We discuss possible sources of this offset, including further bias corrections, “downsizing” in SMBH mass assembly, and preferential SMBH growth. Our results highlight the need to reduce uncertainties from selection and measurement bias in SMBH and stellar masses at all redshifts.

Observations have found black holes spanning 10 orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is, however, provisional as its behavior at infinity is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole’s interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over 0 < z ≲ 2.5. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at z ≲ 7, black holes contribute an effectively constant cosmological energy density to Friedmann’s equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of Ω_Λ measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at z ∼ 0.7.

The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since z ∼ 1 can help to diagnose the origins of locally observed correlations between SMBH mass and stellar mass. We therefore construct three samples of elliptical galaxies, one at z ∼ 0 and two at 0.7 ≲ z ≲ 2.5, and quantify their relative positions in the M _BH−M _* plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher-redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of 7 between z ∼ 1 and z ∼ 0. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of ∼20 at z ∼ 2. The result is robust against variation in the high- and low-redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at z ≲ 2, or that selection and measurement biases are both underestimated, and depend on redshift.

The study of the extragalactic background light (EBL) in the optical and near-infrared has received a lot of attention in the last decade, especially near the wavelength λ ≈ 3.4 μm, with remaining tension among different techniques for estimating the background. In this paper we present a measurement of the contribution of galaxies to the EBL at 3.4 μm that is based on the measurement of the luminosity function (LF) in Lake et al. and the mean spectral energy distribution of galaxies in Lake & Wright. The mean and standard deviation of our most reliable Bayesian posterior chain gives a 3.4 μm background of I _ν = 9.0 ± 0.5 kJy sr⁻¹ (νI _ν = 8.0 ± 0.4 nW m⁻² sr⁻¹ e-fold⁻¹), with systematic uncertainties unlikely to be greater than 2 kJy sr⁻¹. This result is higher than most previous efforts to measure the contribution of galaxies to the 3.4 μm EBL, but is consistent with the upper limits placed by blazars and the most recent direct measurements of the total 3.4 μm EBL.