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Sh 2-235 complex, Auriga

Sh 2-235 complex, Auriga

530 mm f/5 8 hours, February 2013, Photograph

Sh 2-235 complex — This complex of HII regions includes Sh 2-231, Sh 2-232, Sh 2-233 and Sh 2-235. Although these regions appear isolated from one another, they all are thought to be a part of the giant molecular cloud G174+2.5. Shock waves, expanding away from these regions, have significantly changed the kinematic structure of the cloud. The complex is a site of active star formation, and objects at various stages of this process are observed there. The complex is situated at a distance between 1.6 kpc and 2.5 kpc in the Perseus Spiral Arm. From Kirsanova et al., "Star formation around the HII region Sh 2-235", Monthly Notices of the Royal Astronomical Society, 388(2):729-736, 2008 August.

Sh 2-231 and Sh 2-232 — Sh 2-231 and Sh 2-232 are extended, low density, well evolved HII regions. Sh 2-231 is excited by the O9V main-sequence star CGO 103, while Sh 2-232 is excited by the O9.5III giant SB1 spectroscoptic binary HD 37737. HD 37737 has an orbital period of 7.84 days, a surface temperature of 29800 K and an adopted distance of 1.6 kpc. From McSwain et al., "A spectroscopic study of field and runaway OB stars", The Astrophysical Journal, 655:473-483, 2007 January.

Sh 2-233 — The HII region Sh 2-233 is excited by an uncataloged B1.5II bright giant star. From Hunter et al., "Small Galactic HII regions: I. Spectral classifications of massive stars", The Astronomical Journal, 99(3):846-856, 1990 March.

S233IR — The small HII region S233IR contains several manifestations of star formation including masers, molecular outflows, giant molecular cloud cores, young stellar objects, young stellar clusters and an IRAS source. The region is located at a distance of 1.8 kpc. Age estimates are 3 Myr or less for the young stellar clusters and 6 Myr for the field stars. From Porras et al., "Young stellar clusters and H2 nebulosities in S233IR", Astronomy & Astrophysics, 361(2):660-670, 2000 September.

Sh 2-235 — The HII region Sh 2-235 is excited by the O9.5V main-sequence star BD+35°1201. The region is surrounded by a shell-like envelope of molecular gas with dense clumps at the eastern and southern sides. The shell circles the ionization front and is separated from the HII region by a photodissociation region (PDR) visible in mid-infrared. The dense molecular clumps contain young stellar clusters not yet seen at visible wavelengths. The expansion of Sh 2-235 is thought to be responsible for the formation of these clusters. From Kirsanova et al., "Star formation around the HII region Sh 2-235", Monthly Notices of the Royal Astronomical Society, 388(2):729-736, 2008 August.

S235A-B — The star-forming complex S235A-B lies south of the more extended and diffuse HII region Sh 2-235. The small HII region S235A lies at the northern edge of a molecular clump. Lying south of S235A at the south edge of the molecular core, S235B is a smaller region composed of a young star with an expanding ionized envelope surrounded by diffiuse nebulosity. Infrared and radio observations reveal a candidate young stellar object (YSO) between S235A and Sh235B that exhibits two molecular outflows, a hot molecular core, a sub-millimeter peak and a water maser. From Felli et al., "New signposts of massive star formation in the S235A-B region", Astronomy & Astrophysics, 453:911-922, 2006.

Coordinates: RA 5h 41.5m, Dec +36° 7’, PA +0° 12’
Field of view: 1° 56’ x 1° 28’
Image scale: 4.2” / pixel

Date: February 2013
Location: Santa Lucia Range, California
Exposure: 12 x 40 minutes (8 hours), binned 2 x 2 at -20° C

Zenith SQM: 21.6 mag / "²
Guiding error: 0.8" rms
Star FWHM: 4.5", histogram
Star eccentricity: 0.37
Camera noise: 15 e- rms
Background noise: 20 e- rms
Subframe location: 151 e-
Subframe scale: 32 e-

Telescope: Takahashi FSQ-106EDX 530 mm f/5
Camera: Quantum Scientific Imaging 683wsg
Filter: Astrodon H-alpha, 3 nm bandwidth
Focuser: Spike-a Bahtinov Mask
Guider: Santa Barbara Instrument Group ST-i
Flats: Alnitak Astrosystems Flat-Man
USB: Icron Ranger 2122, Moxa UPort 404
Mount: Takahashi EM-400 Temma2M
Acquisition: Diffraction Limited MaxIm DL, CCDAstro Temma, ASCOM Platform
Processing: Pleiades Astrophoto PixInsight, MathWorks MATLAB, IHRP Platform