Publications of the Astronomical Society of the Pacific

van Dokkum, Pieter; Lokhorst, Deborah; Danieli, Shany; Li, Jiaxuan; Merritt, Allison; Abraham, Roberto; Gilhuly, Colleen; Greco, Johnny P.; Liu, Qing

doi: 10.1088/1538-3873/ab9416pmid: N/A

We describe an empirical, self-contained method to isolate faint, large-scale emission in imaging data of low spatial resolution. Multi-resolution filtering (MRF) uses independent data of superior spatial resolution and point source depth to create a model for all compact and high surface brightness objects in the field. This model is convolved with an appropriate kernel and subtracted from the low resolution image. The halos of bright stars are removed in a separate step and artifacts are masked. The resulting image only contains extended emission fainter than a pre-defined surface brightness limit. The method was developed for the Dragonfly Telephoto Array, which produces images that have excellent low surface brightness sensitivity but poor spatial resolution. We demonstrate the MRF technique using Dragonfly images of a satellite of the spiral galaxy M101, the tidal debris surrounding M51, two ultra-diffuse galaxies in the Coma cluster, and the galaxy NGC 5907. As part of the analysis we present a newly-identified very faint galaxy in the filtered Dragonfly image of the M101 field. We also discuss variations of the technique for cases when no low resolution data are available (self-MRF and cross-MRF). The method is implemented in mrf, an open-source MIT licensed Python package (https://github.com/AstroJacobLi/mrf).

Rao, N. Kameswara; Lambert, David L.; Reddy, Arumalla B. S.; García-Hernández, D. A.; Manchado, Arturo; Díaz-Luis, J. J.

doi: 10.1088/1538-3873/ab9097pmid: N/A

We have detected CH+ and CH molecular absorption lines from the youngcompact planetary nebula IC 4997 from high resolution optical spectra. A high-resolution infra-red (H and K bands) spectrum provides detection of H2 emission lines among many other lines. The H2 lines provide an excitation temperature of 2100 K which may result from UV fluorescence in the envelope or from shocks formed at the interface between an expanding outflow of ionized gas and the neutral envelope ejected when the star was on the AGB. It is suggested that the CH+ may result from the endothermic reaction C + H2 → CH+ + H. Intriguingly, CH+ and also CH show a higher expansion velocity than H2 emission suggesting they may be part of the post-shocked gas.

Wang, De-Hua; Zhang, Cheng-Min; Wang, Shuang-Qiang

doi: 10.1088/1538-3873/ab9077pmid: N/A

We analyze the properties of the binary millisecond pulsars (BMSPs), detected at radio and γ-ray wavelengths, and further probe their correlations with the binary orbital parameters and companion masses to trace the possible evolutionary histories. We find that the BMSPs with the lowest-mass companions, (0.006–0.06)M⊙, have short orbital periods Porb < 1 day and in most cases (23 out of 25) have been detected in both radio and γ-rays. On the other hand, the BMSPs with companion masses Mc = (0.06–0.4)M⊙ have a much larger Porb range, from 0.1 to 200 days, and nearly half of them show radio+γ (53 out of 103), while the remaining ones emit only radio waves. We suggest that the two groups, with low-mass and more massive companions, respectively, experienced different evolutionary histories. Concerning the sources with the more massive companions, the radio+γ BMSPs have on average significantly shorter spin periods ( ms) than the radio-only BMSPs ( ms). We propose that the latter systems are a later evolutionary phase of the former ones.

Kaltcheva, Nadia; Paunzen, Ernst; Prišegen, Michal; Golev, Valeri; Watson, Michael

doi: 10.1088/1538-3873/ab8ccepmid: N/A

We combine Strömgren–Crawford uvbyβ photometry with Gaia-DR2 parallaxes for a sample of 880 supergiants of O-B9 spectral types to explore the potential of these data in providing physical parameters of such stars. We obtained reddening corrections and photometric absolute magnitudes via the existing uvbyβ calibrations. We calculated Gaia-based absolute magnitudes applying individual photometric reddening corrections for each star. The uvbyβ photometry is particularly useful in this case, since it provides color excess independent of spectral classification, thus overcoming possible MK classification inconsistencies. After evaluating and correcting the effect of luminosity class mis-classifications on the photometric absolute magnitudes, we found a reasonable agreement between the photometric and Gaia-based absolute magnitudes for this sample. At this point, the color–magnitude MVversus (b − y)0 diagrams based on photometry and Gaia show slight discrepancies, which have to be addressed in the light of the next Gaia data releases. The derived precise reddening corrections should further help to refine the physical parameters of these stars and address their connection to OB-associations and regions of star formation.

Rybizki, Jan; Demleitner, Markus; Bailer-Jones, Coryn; Tio, Piero Dal; Cantat-Gaudin, Tristan; Fouesneau, Morgan; Chen, Yang; Andrae, René; Girardi, Léo; Sharma, Sanjib

doi: 10.1088/1538-3873/ab8cb0pmid:

Tsuchikawa, Takuro; Kaneda, Hidehiro; Ishihara, Daisuke; Kokusho, Takuma; Wada, Takehiko

doi: 10.1088/1538-3873/ab8aa8pmid: N/A

Mid-infrared (IR) array detectors have been used for astronomical observations in space. However, the uniformities of their spectral response curves have not been investigated in detail, the understanding of which is important for spectroscopic observations using large array formats. We characterize the spectral responses of all the pixels in IR array detectors using a Fourier transform infrared spectrometer and cryogenic optics for measurements at high signal-to-noise ratios. We measured the spectral responses of the Si:As impurity band conduction (IBC) array, a flight back-up detector for AKARI/InfraRed Camera. As a result, we find that the Si:As array has intrinsic variations in the spectral response along the row and column directions of the array. We also find that the cutoff wavelength of the Si:As IBC array depends on the intensity of the incident light.

Freudenburg, Jenna K. C.; Givans, Jahmour J.; Choi, Ami; Hirata, Christopher M.; Bennett, Chris; Cheung, Stephanie; Cillis, Analia; Cottingham, Dave; Hill, Robert J.; Mah, Jon; Meier, Lane

doi: 10.1088/1538-3873/ab9503

Huang, Weirong; Xie, Zhou; Zhong, Wenjie; Mei, Ying; Deng, Hui; Liu, Yingbo; Wang, Feng

doi: 10.1088/1538-3873/ab8e9bpmid: N/A

The primary task of the 1.26 m telescope jointly operated by the National Astronomical Observatory and Guangzhou University is photometric observations of the g, r, and i bands. A data processing pipeline system was set up with mature software packages, such as IRAF, SExtractor, and SCAMP, to process approximately 5 GB of observational data automatically every day. However, the success ratio was significantly reduced when processing blurred images owing to telescope tracking error; this, in turn, significantly constrained the output of the telescope. We propose a robust automated photometric pipeline (RAPP) software that can correctly process blurred images. Two key techniques are presented in detail: blurred star enhancement and robust image matching. A series of tests proved that RAPP not only achieves a photometric success ratio and precision comparable to those of IRAF but also significantly reduces the data processing load and improves the efficiency.