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We used high-resolution [C II] 158 $\mu$m mapping of two nebulae IC 59 and IC 63 from SOFIA/upGREAT in conjunction with ancillary data on the gas, dust, and polarization to probe the kinematics, structure, and magnetic properties of their photo-dissociation regions (PDRs). The nebulae are part of the Sh 2-185 H II region illuminated by the B0 IVe star $\gamma$ Cas. The velocity structure of each PDR changes with distance from $\gamma$ Cas, consistent with driving by the radiation. Based on previous FUV flux measurements of, and the known distance to $\gamma$ Cas along with the predictions of 3D distances to the clouds, we estimated the FUV radiation field strength (G0) at the clouds. Assuming negligible extinction between the star and clouds, we find their 3D distances from $\gamma$ Cas. For IC 63, our results are consistent with earlier estimates of distance from Andersson et al. (2013), locating the cloud at 2 pc from $\gamma$ Cas, at an angle of 58 to the plane of the sky, behind the star. For IC 59, we derive a distance of 4.5 pc at an angle of 70 in front of the star. We do not detect any significant correlation between the orientation of the magnetic field (Soam et al. 2017) and the velocity gradients of [C II] gas, indicating a moderate magnetic field strength. The kinetic energy in IC 63 is estimated to be order of ten higher than the magnetic energies. This suggests that kinetic pressure in this nebula is dominant.

Nearly all current simulations predict that outcomes of the star formation process, such as the fraction of stars that form in bound clusters (Gamma), depend on the intensity of star formation activity (SigmaSFR) in the host galaxy. The exact shape and strength of the predicted correlations, however, vary from simulation to simulation. Observational results also remain unclear at this time, because most works have mixed estimates made from very young clusters for galaxies with higher SigmaSFR with those from older clusters for galaxies with lower SigmaSFR. The three blue compact dwarf (BCD) galaxies ESO185-IG13, ESO338-IG04, and Haro11 have played a central role on the observational side because they have some of the highest known SigmaSFR and published values of Gamma. We present new estimates of Gamma for these BCDs in three age intervals (1-10 Myr, 10-100 Myr, 100-400 Myr), based on age-dating which includes Halpha photometry to better discriminate between clusters younger and older than ~10 Myr. We find significantly lower values for Gamma (1-10 Myr) than published previously. The likely reason for the discrepancy is that previous estimates appear to be based on age-reddening results that underestimated ages and overestimated reddening for many clusters, artificially boosting Gamma (1-10 Myr). We also find that fewer stars remain in clusters over time, with ~15-39% in 1-10 Myr, ~5-7% in 10-100 Myr, and ~1-2% in 100-400 Myr clusters. We find no evidence that Gamma increases with SigmaSFR. These results imply that cluster formation efficiency does not vary with star formation intensity in the host galaxy. If confirmed, our results will help guide future assumptions in galaxy-scale simulations of cluster formation and evolution., Comment: Accepted for publication in ApJ

Optical and infrared continuum polarization from the interstellar medium is driven by radiative processes aligning the grains with the magnetic field. While a quantitative, predictive theory of Radiative Alignment Torques (RAT) exists and has been extensively tested, several parameters of the theory remain to be fully constrained. In a recent paper, \citet{medan2019} showed that the polarization efficiency (and therefore grain alignment efficiency) at different locations in the wall of the Local Bubble (LB) could be modeled as proportional to the integrated light intensity from the surrounding stars and OB associations. Here we probe that relationship at high radiation field intensities by studying the extinction and polarization in the two reflection nebulae IC\,59 and IC\,63 in the Sh 2-185 H II region, illuminated by the B0 IV star $\gamma$ Cassiopeia. We combine archival visual polarimetry with new 7-band photometry in the Vilnius system, to derive the polarization efficiency from the material. We find that the same linear relationship seen in the Local Bubble wall also applies to the Sh 2-185 region, strengthening the conclusion from the earlier study., Comment: 31 pages, 11 figures, 4 tables (data under tables will be uploaded to CDS), Accepted for publication in AJ

The optical and near-infrared (OIR) polarization of starlight is typically understood to arise from the dichroic extinction of that light by dust grains whose axes are aligned with respect to a local magnetic-field. The size distribution of the aligned-grain population can be constrained by measurements of the wavelength dependence of the polarization. The leading physical model for producing the alignment is radiative alignment-torques (RAT), which predicts that the most efficiently aligned grains are those with sizes larger than the wavelengths of light composing the local radiation field. Therefore, for a given grain-size distribution, the wavelength at which the polarization reaches a maximum ($\lambda_\mathrm{max}$) should correlate with the characteristic reddening along the line of sight between the dust grains and the illumination source. A correlation between $\lambda_\mathrm{max}$ and reddening has been previously established for extinctions up to $A_V\approx4$ mag. We extend the study of this relationship to a larger sample of stars in the Taurus cloud complex, including extinctions $A_V>10$ mag. We confirm the earlier results for $A_V<4$ mag, but find that the $\lambda_\mathrm{max}$ vs. $A_V$ relationship bifurcates above $A_V\approx4$ mag, with part of the sample continuing the previously observed relationship and the remaining part exhibiting a significantly steeper rise. We propose that the data exhibiting the steep rise represent lines-of-sight towards high density "clumps," where grain coagulation has taken place. We present RAT-based modeling supporting these hypotheses. These results indicate that multi-band OIR polarimetry is a powerful tool for tracing grain growth in molecular clouds, independent of uncertainties in the dust temperature and emissivity., Comment: 25 pages, 7 figures, to be published in ApJ