Romano Corradi

2 Romano Corradi

Astronomical pictures and videos

Planetary nebulae

	An image of NGC 6543, the Cat's Eye Nebula, obtained at the 2.6m Nordic Optical Telescope on summer 2002. Also in the Astronomy Picture of the Day of September 4, 2002.
	Details of the inner regions of the nebula in the previous picture, NGC 6543, at the high resolution provided by the ACS camera on board of the Hubble Space Telescope (images from the HST archive). Green is [OIII], and red is Ha+[NII].
	The very old planetary nebula Sharpless 2-200 in Ha+[NII]. For an image of the extended emission structure around this nebula and other ones, see our PNe haloes database.
	The bipolar planetary nebula NGC 6302. This is an unpublished, deep Ha+[NII] image obtained on 1991 with Hugo Schwarz at the 3.6m ESO telescope. In the collimated outflows of this class of objects, gas is expanding at a velocity one order of magnitude larger than in more spherical planetary nebulae. In the specific case of NGC 6302, expansion velocities larger than 160 km/s have been measured.
	The old bipolar planetary nebula MRSL 252. This [NII] image was obtained at the 3.5m NTT, and the nebula rescued from a catalogue of Galactic HII regions and recognised to be an evolved planetary nebula. It is also one of the largest planetary nebulae known, with a size of 4 parsec and extremely high helium and nitrogen abundances. See Corradi, Villaver, Mampaso and Perinotto (1997, A&A 324, 276) for more details.
	K 4-47, a highly collimated outflow from a dying sun. Red is [NII] emission, green is [OIII]. The nebula seems to be composed of two bullets of gas ejected with a velocity of 150 km/s (from Corradi, Goncalves, Villaver, Mampaso & Perinotto 2000, ApJ 535, 823).
	NGC 6337 is another nebula with several interesting low-ionization structures, studied in the article mentioned for K 4-47. Some of the outer filaments have large expansion velocities of 200 km/s, and the morphology and velocity field suggest that we are looking at a bipolar PN seen pole-on.
	An image of NGC 6853, the Dumbell nebula, obtained at the 2.6m Nordic Optical Telescope by Thomas Augusteijn on autumn 2002 with the new mosaic camera MOSCA. The picture is a combination of B (blue), V (green), and R (red) broad-band images.
	The same nebula as above, in a drawing from 1850 by Padre Angelo Secchi!
	More coming soon.....

Symbiotic stars

	[NII] HST image of He 2-104. We show here the whole nebula with the two nested sets of bipolar lobes and the polar jets. This picture is from HST Press Release STScI-PRC99-32 of August 24, 1999, where other images can be found. Also in the Astronomy Picture of the Day of August 31, 1999. Our recent study (Corradi, Livio, Balick, Munari A& Schwarz 2001, ApJ 553, 211) has demostrated that all the three different outflows from the central binary system, namely the inner and outer lobes, and the polar jets, have been ejected at the same time. This is a puzzling result, as theories do not predict the formation of simultaneous, coeval outflows with different degress of collimation.
	Details of the inner lobes of He 2-104, after drizzling dithered [NII] HST images.
	[NII] HST image of He 2-147. Here we have a Mira with a longer pulsation period and cooler temperature that average field Miras, with a white dwarf companion which is very slowly retracing from a long thermonuclear outburst, as the the Mira's continuum is only now marginally visible in red spectra at lambdas >600 nm, while it was not visibile at all 40 yr ago because of the veiling continuum by the circumstellar ionized material. When the object was discovered in the 60's, the WD was already in outburst so it is not clear when the later started. According to Corradi, Ferrer, Schwarz, Brandi & Garcia (1999, A&A 348, 978) the nebula is a ring inclined at 55 deg on the plane of the sky, expanding at 100 km/sec and with a kinematical age of about 300 yr. There is one symbiotic nova, AG Peg, which outburst is known to have lasted at least 130 years. The outburst of He 2-147 appears in a much later phase than that of AG Peg, where Wolf-Rayet features from the surface of the outbursting WD are now visible, while in He 2-147 the lower ionization and retreating nebular lines might suggest a progressive cooling of the WD. If the outbursts of the two objects are similar, than that of He 2-147 must have begun much earlier than 130 yr ago, and possbily be the ultimate casue of the ejection of the observed ring nebula.
	Page with an artistic animation (mpeg) of a symbiotic system and snapshot frames of the video (tif).
	R Aqr (will come soon)

Other objects

	M 33, the Triangulum galaxy. This is an image that I have taken in 1998 together with Laura Magrini, Antonio Mampaso & Mario Perinotto with the Wide Field Camera at the 2.5m Isaac Newton Telescope. The image is a composition of frames taken in three narrow bands: the green colour represents the galaxian emission in a filter centred on the [OIII] nebular line at 500.7nm, red is the H-alpha hydrogen emission at 656.3nm, while blue is mainly stellar light taken through a continuum filter centred at 555.0nm (Stromgren Y). In only one observing night, and with two positionings of the telescope, it was possible to cover the whole galaxy which has a size of approximately one degree in the sky. The main scientific goal of these observations was to search for planetary nebulae in this nearby galaxy. They are recognised as emission-line objects with generally intense [OIII] and H-alpha lines, negligible continuum emission, and a point-like appearance (1 arcsec corresponds to about 4 pc at the distance of M33). 134 new planetary nebulae were discovered (Magrini et al. 2000, A&A 355, 713), but these observations also contain a large amount of information about other ionised nebulae, such as HII regions, supernova remnants, Be stars, symbiotic binaries, Wolf-Rayet stars, LBVs, etc. The image is also available at higher resolution (TIF (38 M), PDF (2 M)).
	Sextans B galaxy. A search for emission-line objects was also done in the dwarf irregular galaxy Sextans B during our ongoing survey of the Local Group (the "Local Group Census"). In this relatively small galaxy located at the outer fringes of the Local Group, at a distance of almost 5 million light years, 5 planetary nebulae were discovered and studied (Magrini et al. 2002, A&A 386, 869).
	V848 Monocerotis (coming soon)

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Last updated on December 2002
Romano L.M. Corradi/ rcorradi@ing.iac.es