The stellar mass function is assumed to be constant through time. If it is constant, then the flux contribution to HII regions from hot, high mass stars would remain uniform with redshift. If this contribution has changed, then the mean H ii region temperature would change with increasing redshift. To quantify how mean stellar temperature may have evolved with time, we mapped the temperature of H ii regions to a redshift of about z = 0.7 using SDSS spectral data. We find no distance dependence with temperature.

Broadband photometric redshifts are routinely obtained for galaxies to estimate their distances. While effective for many uses, the common resolution in z of 0.01–0.02 is too coarse for detailed large-scale structure mapping, particularly in low-density volumes where the galaxy distribution is least understood. To map galaxies in these low-density volumes, and noting that the percentage of galaxies having emission tends to rise as number density decreases, we have designed a filter system to photometrically measure the redshifts of galaxies with emission. The system consists of two “ramp” filters that cover a common wavelength range with transmission curves sloping from blue to red and from red to blue respectively. This causes the intensity of the image through either filter to be a function of the wavelength of the emission line. A third filter with a bandpass to the side is used to measure and remove the continuum. We have obtained a set of such filters that are tuned for isolating Hα in the redshift range of 3,000–9,000 km s−1. Simulated photometry, applied to spectra of 197 emission-line galaxies from the SDSS, shows the accuracy of the method to be between 250 and 620 km s−1, depending on line strength. Actual photometry of a sample of 16 active galaxies measured their redshifts with an accuracy of 573 km s−1. This is approximately an order of magnitude more accurate than broadband photometric redshifts. We discuss the errors inherent in this method and present ways to modify the filter set to further improve accuracy.

As part of a series of studies that integrate new and existing observations with innovative analysis as demonstrations for how the new ODIN (Optical Delving Infrared iNnovation)
facility will be used, we examine early results that establish the potential of polarization signatures as a new method of performing Space Situational Awareness (SSA) analysis. We will show ways in which the polarization data supports existing methods for extracting signature features that correlate well with photometric methods. Also, importantly, we will show feature extractions that cannot be done with existing methods. We know that some features in brightness are caused by near-glint reflection off solar panels, while others are small amplitude glints off minor support structures or from facets or edges on the main body of the spacecraft. We see polarization features from all of these constructions. We conclude that polarization studies will significantly aid the detailed interpretation of physical structures such as solar panels, facets, and communications antennae via non-resolved observations. Thus, polarization is an important complement to photometric observations.

Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios.

Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration.

Results. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of ∼0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was ∼3 CU, and the peak of the high-energy spectral component was found to be at ∼2 TeV. Both the X-ray and VHE gamma-ray spectral slopes were measured to be extremely hard, with spectral indices < 2 during most of the observing campaign, regardless of the X-ray and VHE flux. This study reports the hardest Mrk 501 VHE spectra measured to date. The fractional variability was found to increase with energy, with the highest variability occurring at VHE. Using the complete data set, we found correlation between the X-ray and VHE bands; however, if the June 9 flare is excluded, the correlation disappears (significance < 3σ) despite the existence of substantial variability in the X-ray and VHE bands throughout the campaign.

Conclusions. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency-peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The data set acquired shows that the broadband spectral energy distribution (SED) of Mrk 501, and its transient evolution, is very complex, requiring, within the framework of synchrotron self-Compton (SSC) models, various emission regions for a satisfactory description. Nevertheless the one-zone SSC scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behavior seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays.

We present the first results from a reverberation-mapping campaign undertaken during the first half of 2012, with additional data on one active galactic nucleus (AGN) (NGC 3227) from a 2014 campaign. Our main goals are (1) to determine the black hole masses from continuum-H β reverberation signatures, and (2) to look for velocity-dependent time delays that might be indicators of the gross kinematics of the broad-line region. We successfully measure H β time delays and black hole masses for five AGNs, four of which have previous reverberation mass measurements. The values measured here are in agreement with earlier estimates, though there is some intrinsic scatter beyond the formal measurement errors. We observe velocity-dependent H β lags in each case, and find that the patterns have changed in the intervening five years for three AGNs that were also observed in 2007.

Space Situational Awareness (SSA) observations are sometimes performed through a spectral filter. The traditional filters used are those of the Johnson-Cousins photometric system (B, V, R, and I). The SSA community has been observing with these filters for decades and therefore has historical data spanning this duration. More recently, the astronomical community is replacing the Johnson-Cousins system with the Sloan photometric system as the primary system for optical observations. The most recent large astronomical surveys in the optical regime have used the Sloan filters: the Sloan Digital Sky Survey and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). The Pan-STARRS 1 catalog sky coverage and its astrometric and photometric precision make it well suited for in-frame calibrations of satellite observations. Such in-frame calibrations would provide increased calibration cadence and the potential for improving accuracy by mitigating the effects of a changing atmosphere. Because a comparable catalog in the Johnson-Cousins photometric system that would allow in-frame calibrations does not exist, it makes sense for SSA observations to transition to the Sloan system. A consequence of transitioning from Johnson-Cousins to Sloan is the obsolescence of the historical Johnson-Cousins satellite photometry. To compare photometry between the Johnson-Cousins and Sloan systems, a transformation needs to be made to convert data from one photometric system to another.
A number of such transformations exist within the astronomical community for stellar objects. However, the Spectral Energy Distributions (SEDs) of stars are not the same as those of satellites. Reflection for spacecraft can be modeled based on diffuse and specular reflection components, where the diffuse components’ reflected spectrum may have spectral characteristics of the material off which it reflects, thereby altering the SED from that of the Sun. While the SEDs of stars are largely static, the SEDs of satellites are not. Specifically, their SED may change with phase angle (e.g., solar panel contributions are phase angle dependent and typically make the SED bluer). To investigate the transformation between Johnson-Cousins and Sloan for satellites, we performed the following analysis. We observed four satellites sequentially in Johnson-Cousins filters (B, V, R, and I) and Sloan filters (g, r, i, and z), covering a large range of phase angle. We then empirically derived transformations between Johnson-Cousins and Sloan for each satellite’s observed data and for all of the observed satellite data as a whole, and juxtaposed these with an astronomical transformation. We found mixed results for the transformation relations. The r – V as a function of V – R relation provides a great fit for all of the observed satellite data with low root mean square (RMS) error and is exactly the same as the astronomical transformation. The r – z as a function of R – I relation provides a great fit for all of the observed satellite data, but has large RMS scatter and is distinct from the astronomical transformation. Thus, we do not recommend transforming historical satellite photometry observed in Johnson-Cousins to Sloan to compare to observations of satellites taken in the Sloan filters. Since the transformations are dependent on the SED of the satellite, and the satellites’ SEDs are variable, transformations generally yielded poor results for the two photometric systems we studied here, i.e. Johnson-Cousins and Sloan. Moreover, our supposition is that such attempts with any two photometric systems may yield similarly poor results.Cousins to Sloan is the obsolescence of the historical Johnson-Cousins satellite photometry. To compare photometry between the Johnson-Cousins and Sloan systems, a transformation needs to be made to convert data from one photometric system to another.
A number of such transformations exist within the astronomical community for stellar objects. However, the Spectral Energy Distributions (SEDs) of stars are not the same as those of satellites. Reflection for spacecraft can be modeled based on diffuse and specular reflection components, where the diffuse components’ reflected spectrum may have spectral characteristics of the material off which it reflects, thereby altering the SED from that of the Sun. While the SEDs of stars are largely static, the SEDs of satellites are not. Specifically, their SED may change with phase angle (e.g., solar panel contributions are phase angle dependent and typically make the SED bluer). To investigate the transformation between Johnson-Cousins and Sloan for satellites, we performed the following analysis. We observed four satellites sequentially in Johnson-Cousins filters (B, V, R, and I) and Sloan filters (g, r, i, and z), covering a large range of phase angle. We then empirically derived transformations between Johnson-Cousins and Sloan for each satellite’s observed data and for all of the observed satellite data as a whole, and juxtaposed these with an astronomical transformation. We found mixed results for the transformation relations. The r – V as a function of V – R relation provides a great fit for all of the observed satellite data with low root mean square (RMS) error and is exactly the same as the astronomical transformation. The r – z as a function of R – I relation provides a great fit for all of the observed satellite data, but has large RMS scatter and is distinct from the astronomical transformation. Thus, we do not recommend transforming historical satellite photometry observed in Johnson-Cousins to Sloan to compare to observations of satellites taken in the Sloan filters. Since the transformations are dependent on the SED of the satellite, and the satellites’ SEDs are variable, transformations generally yielded poor results for the two photometric systems we studied here, i.e. Johnson-Cousins and Sloan. Moreover, our supposition is that such attempts with any two photometric systems may yield similarly poor results.