From Xinglong Observatory [兴隆观测站] (CN): “LAMOST Helps Detect Dust in the Outskirts of Andromeda Galaxy and Triangulum Galaxy” 

LAMOST telescope located in Xinglong Station, Hebei Province, China, Altitude 960 m (3,150 ft).

From Xinglong Observatory [兴隆观测站] (CN)

Chinese Academy of Sciences [中国科学院] (CN)

Mar 18, 2021

XU Ang
The National Astronomical Observatories of China [ 国家天文台] at Chinese Academy of Sciences [中国科学院](CN)

Dust as an annoying thing is quite common in our everyday lives. But the ubiquitous dust in the vast universe is a subject of great interest to astronomers.

A recent work led by Doctoral Candidate ZHANG Ruoyi and Prof. YUAN Haibo from the Department of Astronomy, Beijing Normal University [北京師範大學](CN), reports the detection of dust in the outskirts of Andromeda Galaxy (Messier 31) and Triangulum Galaxy (Messier 33).

Andromeda Galaxy Messier 31 with Messier 32 -a satellite galaxy Credit:Terry Hancock- Down Under Observatory (US).

The Triangulum Galaxy, Messier 33, via The VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile. This beautifully detailed image of the galaxy Messier 33. This nearby spiral, the second closest large galaxy to our own galaxy, the Milky Way, is packed with bright star clusters, and clouds of gas and dust. This picture is amongst the most detailed wide-field views of this object ever taken and shows the many glowing red gas clouds in the spiral arms with particular clarity.

Part of ESO’s Paranal Observatory the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

The results were published in The Astrophysical Journal Letters.

Messier 31 and Messier 33 are the largest and 3rd largest galaxies in the Local Group, respectively.

Local Group. Andrew Z. Colvin 3 March 2011

It is extremely challenging to detect dust in the outskirts of Messier 31 and Messier 33, as their signals are very weak, in terms of either dust absorption in optical and/or emission in far infrared, compared to those of dust in the Milky Way. Therefore, the signals from Galactic foreground dust have to be removed carefully.

Fortunately, thanks to the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), also known as Guoshoujing Telescope, operated by The National Astronomical Observatories of China [ 国家天文台] at Chinese Academy of Sciences [中国科学院](CN), millions of high-quality spectra have been recorded, providing a great opportunity to map the dust distribution in the Milky Way.

Using a sample of about 190,000 stars from the LAMOST and Gaia, the researchers constructed a large and precise two-dimensional foreground dust reddening map toward the M31 and M33 region.

“This foreground dust reddening map tells people how much light is absorbed by dust in the Milky Way,” said ZHANG Ruoyi, the leading author of this study. The map shows the complex structure of dust clouds toward the Messier 31, suggesting that the map should be used for precise foreground reddening corrections for targets in Messier 31.

By carefully removing the foreground reddening from the SFD98 dust reddening map, which contains dust signals from all the Milky Way, Messier 31 and Messier 33, the distribution of dust in the outskirts of Messier 31 and Messier 33 are revealed in great detail to a very large distance. Dust in the Messier 31 and Messier 33 disks extends out to about 2.5 times their optical radii.

The researchers also found that a significant amount of dust in clumpy and filamentary structures exists in the halo of Messier 31, out to a distance of over 100 kiloparsec (1 kiloparsec equals to 3260 light years), which is about 5 times its optical radius.

Where do the dust clouds in the halo come from? Are their properties similar to those in the disk? There are interesting questions to be answered. “Our results combined with future observations, e.g., observations by FAST, will provide new clues on the distributions, properties, and cycling of dust in spiral galaxies,” said Prof. YUAN Haibo, the corresponding author.

Figure: Left: Foreground reddening map of LAMOST. The solid ellipses mark the optical extent of Messier 31, Messier 33, and two satellites Messier 32 and Messier 101. Right: Dust reddening map of Messier 31 and Messier 33. The two dotted ellipses centered on Messier 31 and Messier 33 represent the extent of their dust disks. The large circle centered on Messier 31 represents the extent of its dust halo. Image by ZHANG Ruoyi.

See the full article here .


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Chinese Academy of Sciences-National Astronomical Observatories Xinglong Observatory Station, located in Xinglong Station, Hebei Province, China.

The Xinglong Observatory [兴隆观测站] (CN) of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) (IAU code: 327, coordinates: 40°23′39′′ N, 117°34′30′′ E) was founded in 1968. At present, it is one of most primary observing stations of NAOC. As the largest optical astronomical observatory site in the continent of Asia, it has 9 telescopes with effective aperture larger than 50 cm. These are the Guo Shoujing Telescope, also called the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), the 2.16-m Telescope, a 1.26-m optical & near-infrared telescope, a 1-m Alt-Az telescope, an 85-cm telescope (NAOC-Beijing Normal University [北京師範大學](CN) Telescope, NBT), an 80-cm telescope (Tsinghua University [清华大学](CN)-NAOC Telescope, TNT), a 60-cm telescope, a 50-cm telescope and a 60/90-cm Schmidt telescope.
The average altitude of the Xinglong Observatory is about 900 m. The Xinglong Observatory is located at the south of the main peak of the Yanshan Mountains, in the Xinglong County, Hebei Province, which lies about 120 km (about 2 hours’ drive) to the northeast of Beijing. A shuttle bus runs between NAOC campus and Xinglong Observatory every Tuesday and Friday. The mean and media seeing values of the Xinglong Observatory are 1.9′′ and 1.7′′, respectively. On average, there are 117 photometric nights and 230 observable nights per year based on the data of 2007-2014. Most of the time, the wind speed is less than 4 m/s (the mean value is 2 m/s), and the sky brightness is about 21.1 mag arcsec2 in V band at the zenith.

Each year, more than a hundred astronomers use the telescopes of the Xinglong Observatory to perform the observations for the studies on Galactic sciences (stellar parameters, extinction measurements, Galactic structures, exoplanets, etc.) and extragalactic sciences (including nearby galaxies, AGNs, high-redshift quasars), as well as time-domain astronomy (supernovae, gamma-ray bursts, stellar tidal disruption events, and different types of variable stars). In recent years, besides the basic daily maintenance of the telescopes, new techniques and methods have been explored by the engineers and technicians of the Xinglong Observatory to improve the efficiency of observations. Meanwhile, the Xinglong Observatory is also a National populscience and education base of China for training students from graduate schools, colleges, high schools and other education institutes throughout China, and it has hosted a number of international workshops and summer schools.

The Chinese Academy of Sciences [中国科学院] (CN) is the linchpin of China’s drive to explore and harness high technology and the natural sciences for the benefit of China and the world. Comprising a comprehensive research and development network, a merit-based learned society and a system of higher education, CAS brings together scientists and engineers from China and around the world to address both theoretical and applied problems using world-class scientific and management approaches.

Since its founding, CAS has fulfilled multiple roles — as a national team and a locomotive driving national technological innovation, a pioneer in supporting nationwide S&T development, a think tank delivering S&T advice and a community for training young S&T talent.

Now, as it responds to a nationwide call to put innovation at the heart of China’s development, CAS has further defined its development strategy by emphasizing greater reliance on democratic management, openness and talent in the promotion of innovative research. With the adoption of its Innovation 2020 programme in 2011, the academy has committed to delivering breakthrough science and technology, higher caliber talent and superior scientific advice. As part of the programme, CAS has also requested that each of its institutes define its “strategic niche” — based on an overall analysis of the scientific progress and trends in their own fields both in China and abroad — in order to deploy resources more efficiently and innovate more collectively.

As it builds on its proud record, CAS aims for a bright future as one of the world’s top S&T research and development organizations.