Comparison stars

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High resolution images of the host galaxy of MRK 509

Fig. 1

Fig. 2

Fig. 1: This image shows the oval shaped host galaxy of MRK 509. In addition, a diffuse halo to the

south is visible. [Image credit: MacKenty 1990, ApJS 72, 231 / N up, E left]

Fig. 2: The centre of the quasar host shows the bright AGN, surrounded by a possible starburst ring

(image size 10.4"×10.4")  [Image credit: NASA, ESA, G. Kriss (STScI), and J. de Plaa (SRON

Netherlands Institute for Space Research); Acknowledgment: B. Peterson (Ohio State University)]

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Notes

Markarian 509 (MRK 509 for short) is a bright quasar in south-western Aquarius, close to the constellation Capricornus. MRK 509 was discovered in 1973 as a B=13 mag compact object by the UV-Continuum- Survey run by Markarian et al. (MRK), searching for blue galaxies with excessive UV-emission. Follow-up spectroscopic investigations in 1974 revealed a Seyfert 1-spectrum, which led to the quasar classification. At a distance of only about 400 million light-years, MRK 509 is one of the nearest quasi-stellar objects known. Since 1975, quasar MRK 509 has been noticed as an infrared source, further investigated by IRAS in 1983 and the 2 Micron All Sky Survey (2MASS). As a radio source, this quasar was first detected in 1976. MRK 509 is also known as one of the brightest X-ray AGN in the sky, first detected in 1974-1976 by the 2. Ariel V-Survey (2A). Further X-ray investigations were carried out by HEAO A-1 (1H), ROSAT (RXS), EXOSAT and SWIFT. A hint of the quasar host can be seen in the finding chart above. The host galaxy appears as a star-like object (QSO), enveloped by a diffuse circular halo of about 10”× 8”. However, deep high resolution photographs in the optical revealed a much larger extension and an asymmetric halo to the south (see Fig. 1). As there is no neighbouring galaxy found close by, this asymmetric halo is an indication for a strong interaction in the recent past. In addition, an image by the Hubble Space Telescope (see Fig. 2) shows a ring-like feature around the galaxy core, that possibly represents an irregular starburst ring with an outer radius of <2 kpc. This advanced stage of merger has most likely triggered the strong AGN activity of MRK 509. The central powerhouse of MRK 509 is a supermassive black hole of approximately 3×108 solar masses. In the optical, the quasar host appears very compact and shows an amorphous optical morphology. Perhaps, we see a disturbed and slightly tilted face-on disk galaxy, probably of type S0. The published data on the apparent size of the quasar host are inconsistent. For clarity, the author did some measuring from optical inspection of a deep CCD image in V-band, published by MacKenty (1990) (see Fig. 1). Combined with the scale reference given by NED, the resulting true size of the main galaxy body of the quasar host is about 160×115 klyrs. This is a factor of 7.7 times the size published by Markarian et al. (1973). Including the asymmetric halo to the south, the overall true size increases to about 182×160 klyrs. Quasar MRK 509 is a weakly variable object with a total range of nearly 2 magnitudes in the optical. This object is an attractive target for visual observers with at least an 8-inch telescope or larger. Medium size telescopes show MRK 509 as a stellar object. In large instruments, MRK 509 becomes increasingly star-like with a very faint outer halo. CCD observers, as well as visual observers, shall use the comparison stars given above. Other photometric sequences were published by Doroshenko et al. (2005), Hamilton et al. (1978), Miller (1981), and the BAAVSS. ____________ Quasar MRK 509 is located in south-western Aquarius, close to the constellation Capricornus, and only 1.5° SW of Epsilon Aqr. Two deep sky showpieces around MRK 509 are worth visiting. First there is M72, a bright 9.3-mag globular cluster only 3° to the south-east. A 10-inch telescope will resolve about 20 faint stars of this globular, located about 60 000 light-years away from earth. The second object is NGC 7009, the "Saturn-Nebula", a prominent planetary nebula, located some 5° to the east. Through the eyepiece, NGC 7009 appears as a tiny blue-green oval disk of 30"×26", which responds well to both UHC- and O-III filters.

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Literature

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Links: Chara/PEGA MRK 509 (Sasmirala, Univ. of Heidelberg) BAAVSS

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© Stefan Karge (FQM)  /  last obs. 2024-04-13

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