arXiv subjects

Fengjie Lei

Publications and source records attributed to Fengjie Lei.

5 recordsLinked to original sources

arXiv2020

A Mysterious Ring in Dark Space?

We report the discovery of a low-surface-brightness (27.42 mag arcsec^(-2) in g band) nebula, which has a ring-like shape in the Beijing-Arizona Sky Survey (BASS). Positive detections have been found in multiband data from far ultraviolet to far infrared, except the z band from BASS and W1, W2 from the Wide-field Infrared Survey Explorer. The reddening of the nebula E(B - V) ~ 0.02 mag is estimated from Infrared Astronomical Satellite (IRAS) 100 micron intensity and HI column density. With the help of the 3D reddening map from Pan-STARRS 1, the Two Micron All Sky Survey, and Gaia, the distance to the nebula of about 500 pc from Earth is derived. Such a low-surface-brightness nebula whose energy can be interpreted by the diffuse Galactic light could account for the optical counterpart of the infrared cirrus, which was detected by IRAS more than 30 yr ago. The ring-like structure might be the ultimate phase of an evolved planetary nebula, while the central white dwarf star has been ejected from the nebula for an unclear reason. On the other hand, the ring structure being a superposition of two close filaments might be another reasonable explanation. Considering the lack of spectroscopic data and uncertainty in the distance measurement, these interpretations need to be checked by future observations.

astro-ph.GA↗

arXiv2020

The Third Data Release of the Beijing-Arizona Sky Survey

The Beijing-Arizona Sky Survey (BASS) is a wide and deep imaging survey to cover a 5400 deg$^2$ area in the Northern Galactic Cap with the 2.3m Bok telescope using two filters ($g$ and $r$ bands). The Mosaic $z$-band Legacy Survey (MzLS) covers the same area in $z$ band with the 4m Mayall telescope. These two surveys will be used for spectroscopic targeting of the Dark Energy Spectroscopic Instrument (DESI). The BASS survey observations were completed in 2019 March. This paper describes the third data release (DR3) of BASS, which contains the photometric data from all BASS and MzLS observations between 2015 January and 2019 March. The median astrometric precision relative to {\it Gaia} positions is about 17 mas and the median photometric offset relative to the PanSTARRS1 photometry is within 5 mmag. The median $5σ$ AB magnitude depths for point sources are 24.2, 23.6, and 23.0 mag for $g$, $r$, and $z$ bands, respectively. The photometric depth within the survey area is highly homogeneous, with the difference between the 20\% and 80\% depth less than 0.3 mag. The DR3 data, including raw data, calibrated single-epoch images, single-epoch photometric catalogs, stacked images, and co-added photometric catalogs, are publicly accessible at \url{http://batc.bao.ac.cn/BASS/doku.php?id=datarelease:home}.

astro-ph.GA↗

arXiv2018

The Second Data Release of the Beijing-Arizona Sky Survey

This paper presents the second data release (DR2) of the Beijing-Arizona Sky Survey (BASS). BASS is an imaging survey of about 5400 deg$^2$ in $g$ and $r$ bands using the 2.3 m Bok telescope. DR2 includes the observations as of July 2017 obtained by BASS and Mayall $z$-band Legacy Survey (MzLS). This is our first time to include the MzLS data covering the same area as BASS. BASS and MzLS have respectively completed about 72% and 76% of their observations. The two surveys will be served for the spectroscopic targeting of the upcoming Dark Energy Spectroscopic Instrument. Both BASS and MzLS data are reduced by the same pipeline. We have updated the basic data reduction and photometric methods in DR2. In particular, source detections are performed on stacked images, and photometric measurements are co-added from single-epoch images based on these sources. The median 5$σ$ depths with corrections of the Galactic extinction are 24.05, 23.61, and 23.10 mag for $g$, $r$, and $z$ bands, respectively. The DR2 data products include stacked images, co-added catalogs, and single-epoch images and catalogs. The BASS website (http://batc.bao.ac.cn/BASS/) provides detailed information and links to download the data.

astro-ph.IM↗

arXiv2018

An H$α$ Imaging Survey of the Low-surface-brightness Galaxies Selected from the Fall Sky Region of the 40$\%$ ALFALFA \ion{H}{1} Survey

We present the observed H$α$ flux and derived star formation rates (SFRs) for a fall sample of low$-$surface$-$brightness galaxies (LSBGs). The sample is selected from the fall sky region of the 40$\%$ ALFALFA {\ion{H}{1}} survey $-$ SDSS DR7 photometric data, and all the $Hα$ images were obtained using the 2.16 m telescope, operated by the National Astronomy Observatories, Chinese Academy of Sciences. A total of 111 LSBGs were observed and $Hα$ flux was measured in 92 of them. Though almost all the LSBGs in our sample are {\ion{H}{1}}$-$rich, their SFRs derived from the extinction and filter$-$transmission$-$corrected $Hα$ flux, are less than 1$M_{\sun}$$yr^{-1}$. LSBGs and star forming galaxies have similar {\ion{H}{1}} surface densities, but LSBGs have much lower SFRs and SFR surface densities than star$-$forming galaxies. Our results show that LSBGs deviate from the Kennicutt-Schmidt law significantly, which indicate that they have low star formation efficiency. The SFRs of LSBGs are close to average SFRs in Hubble time and support the previous arguments that most of the LSBGs are stable systems and they tend to seldom contain strong interactions or major mergers during their star formation histories.

astro-ph.GA↗

arXiv2015

Low Surface Brightness Galaxies selected from the 40% sky area of the ALFALFA HI survey.I.Sample and statistical properties

The population of Low Surface Brightness (LSB) galaxies is crucial for understanding the extremes of galaxy formation and evolution of the universe. As LSB galaxies are mostly rich in gas (HI), the alpha.40-SDSS DR7 sample is absolutely one of the best survey combinations to select a sample of them in the local Universe. Since the sky backgrounds are systematically overestimated for galaxy images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended low surface brightness outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images in the alpha.40-SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture and fitted geometric parameters with an exponential profile model for each galaxy image. Basing on the photometric and geometric results, we further calculated the B-band central surface brightness, mu_{0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with mu_{0}(B) > 22.5 mag arcsec^{-2} and the minor-to-major axis ratio b/a > 0.3. This HI-selected LSB galaxy sample from the alpha.40-SDSS DR7 is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in HI observation and the optical magnitude within the limit of SDSS DR7 photometric survey. We made analysis on optical and radio 21cm HI properties of this LSB galaxy sample. Additionally, we statistically investigated the environment of our LSB galaxies, and found that up to 92% of the total LSB galaxies have less than 8 neighbouring galaxies, which strongly evidenced that LSB galaxies prefer to reside in the low-density environment.

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