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We calculate the emission of protoplanetary disks threaded by a poloidal magnetic field and irradiated by the central star. The radial structure of these disks was studied by Shu and collaborators and the vertical structure was studied by Lizano and collaborators. We consider disks around low mass protostars, T Tauri stars, and FU Ori stars with different mass-to-flux ratios $\lambda_{\rm sys}$. We calculate the spectral energy distribution and the antenna temperature profiles at 1 mm and 7 mm convolved with the ALMA and VLA beams. We find that disks with weaker magnetization (high values of $\lambda_{\rm sys}$) emit more than disks with stronger magnetization (low values of $\lambda_{\rm sys}$). This happens because the former are denser, hotter and have larger aspect ratios, receiving more irradiation from the central star. The level of magnetization also affects the optical depth at millimeter wavelengths, being larger for disks with high $\lambda_{\rm sys}$. In general, disks around low mass protostars and T Tauri stars are optically thin at 7 mm while disks around FU Ori are optically thick. A qualitative comparison of the emission of these magnetized disks, including heating by an external envelope, with the observed millimeter antenna temperature profiles of HL Tau indicates that large cm grains are required to increase the optical depth and reproduce the observed 7 mm emission at large radii., Comment: 21 pages, 12 figures

The Sky Quality Meter (SQM) has become the most common device to track the evolution of the brightness of the sky from polluted regions to first class astronomical observatories. A vast database of SQM measurements already exists for many places in the world. Unfortunately, the SQM operates over a wide spectral band and its spectral response interacts with the sky's spectrum in a complex manner. This is why the optical signals are difficult to interpret when the data are recorded in regions with different sources of artificial light. The brightness of the night sky is linked in a complex way to ground-based light emissions while taking into account atmospheric-induced optical distortion as well as spectral transformation from the underlying ground surfaces. While the spectral modulation of the sky's radiance has been recognized, it still remains poorly characterized and quantified. The impact of the SQM's spectral characteristics on the sky brightness measurements is here analysed for different light sources, including low and high pressure sodium lamps, PC-amber and white LEDs, metal halide, and mercury lamps. We show that a routine conversion of radiance to magnitude is difficult or rather impossible because the average wavelength depends on actual atmospheric and environment conditions, the spectrum of the source, and device specific properties. We correlate SQM readings with both the Johnson astronomical photometry bands and the human system of visual perception, assuming different lighting technologies. These findings have direct implications for the processing of SQM data and for its improvement and/or remediation., Comment: Accepted on MNRAS: ref. MN-16-1235-MJ.R2 Accepted 2017 January 17. Received 2017 January 12; in original form 2016 April 15

We model the vertical structure of magnetized accretion disks subject to viscous and resistive heating, and irradiation by the central star. We apply our formalism to the radial structure of magnetized accretion disks threaded by a poloidal magnetic field dragged during the process of star formation developed by Shu and coworkers. We consider disks around low mass protostars, T Tauri, and FU Orionis stars. We consider two levels of disk magnetization, $\lambda_{sys} = 4$ (strongly magnetized disks), and $\lambda_{sys} = 12$ (weakly magnetized disks). The rotation rates of strongly magnetized disks have large deviations from Keplerian rotation. In these models, resistive heating dominates the thermal structure for the FU Ori disk. The T Tauri disk is very thin and cold because it is strongly compressed by magnetic pressure; it may be too thin compared with observations. Instead, in the weakly magnetized disks, rotation velocities are close to Keplerian, and resistive heating is always less than 7\% of the viscous heating. In these models, the T Tauri disk has a larger aspect ratio, consistent with that inferred from observations. All the disks have spatially extended hot atmospheres where the irradiation flux is absorbed, although most of the mass ($\sim 90-95$ \%) is in the disk midplane. With the advent of ALMA one expects direct measurements of magnetic fields and their morphology at disk scales. It will then be possible to determine the mass-to-flux ratio of magnetized accretion disks around young stars, an essential parameter for their structure and evolution. Our models contribute to the understanding of the vertical structure and emission of these disks., Comment: 37 pages, 8 figures