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NGC 205
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Title: Discovery of true, likely and possible symbiotic stars in the dwarf spheroidal NGC 205
Author: Denise R. Gonçalves, Laura Magrini, Ignacio G. de la Rosa, Stavros Akras

In this paper we discuss the photometric and spectroscopic observations of newly discovered (symbiotic) systems in the dwarf spheroidal galaxy NGC 205. The Gemini Multi-Object Spectrograph on-off band [O III] 5007 A emission imaging highlighted several [O III] line emitters, for which optical spectra were then obtained (Goncalves et al. 2014). The detailed study of the spectra of three objects allow us to identify them as true, likely and possible symbiotic systems (SySts), the first ones discovered in this galaxy. SySt-1 is unambiguously classified as a symbiotic star, because of the presence of unique emission lines which belong only to symbiotic spectra, the well known O VI Raman scattered lines. SySt-2 is only possibly a SySt because the Ne VII Raman scattered line at 4881 A, recently identified in a well studied Galactic symbiotic as another very conspicuous property of symbiotic, could as well be identified as N III or [Fe III]. Finally, SySt-3 is likely a symbiotic binary because in the red part of the spectrum it shows the continuum of a late giant, and forbidden lines of moderate- to high-ionisation, like [Fe v] 4180 A. The main source for skepticism on the symbiotic nature of the latter systems is their location in the PN region in the [O III] 4363/H\gamma\ vs [O III] 5007/H\beta\ diagnostic diagram (Gutierrez-Moreno et al. 1995). It is worth mentioning that at least another two confirmed symbiotics, one of the Local Group dwarf spheroidal IC 10 and the other of the Galaxy, are also misplaced in this diagram.

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Messier 110
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NGC 205 (also Messier 110, M 110, The Edward Young Star, IRAS 00376+4124, MCG 7-2-14, UGC 426 and PGC 2429) is a magnitude +8.92 dwarf elliptical galaxy located 2,690 ±90 thousand light-years away away in the constellation Andromeda.
NGC 205 is a satellite galaxy of Messier 31, the Andromeda Galaxy.

The galaxy was discovered by French astronomer Charles Messier using a 8.38 cm (3.3-inch) refracting telescope at the Hôtel de Cluny (now the Musée national du Moyen Age), in Paris, France on the 10th August 1773.
The galaxy was independently discovered by Caroline Herschel on August 27, 1783.

Right Ascension 00h 40m 22.1s, Declination +41° 41' 07"

Unlike M32, NGC205 does not show evidence for a supermassive black hole at its center.
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Title: Near-infrared properties of asymptotic giant branch stars in nearby dwarf elliptical Galaxy NGC 205
Authors: M.Y. Jung, Jongwan Ko, Jae-Woo Kim, Sang-Hyun Chun, Ho-Il Kim, Y.-J. Sohn

We investigated the distribution of resolved asymptotic giant branch (AGB) stars over a much larger area than covered by previous near-infrared studies in the nearby dwarf elliptical galaxy NGC 205. Using data obtained with the WIRCam near-infrared imager of the CFHT, we selected the AGB stars in the JHKs colour-magnitude diagrams, and separated the C stars from M-giant stars in the JHKs colour-colour diagram. We identified 1,550 C stars in NGC 205 with a mean absolute magnitude of M_Ks = -7.49 ± 0.54, and colours of (J - Ks) = 1.81 ± 0.41 and (H - Ks) = 0.76 ± 0.24. The ratio of C stars to M-giant stars was estimated to be 0.15 ± 0.01 in NGC 205, and the local C/M ratios for the southern region are somewhat lower than those for the northern region. The (J - Ks) colour distributions of AGB stars contain the main peak of the M-giant stars and the red tail of the C stars. A comparison of the theoretical isochrone models with the observed colour distribution indicates that most of the bright M-giant stars in NGC 205 were formed at log(t_yr) ~ 9.0-9.7. The logarithmic slope of the M_Ks luminosity function for M-giant stars was estimated to be 0.84 ± 0.01, which is comparable with dwarf elliptical galaxies NGC 147 and NGC 185. Furthermore, we found that the logarithmic slopes of the M_Ks luminosity function for C and M-giant stars are different to places, implying a different star formation history within NGC 205. The bolometric luminosity function for M-giant stars extends to M_bol = -6.0 mag, and that for C stars spans -5.6 < M_bol < -3.0. The bolometric luminosity function of C stars is unlikely to be a Gaussian distribution and the mean bolometric magnitude of C stars is estimated to be M_bol = -4.24 ± 0.55, which is consistent with our results for dwarf elliptical galaxies NGC 147 and NGC 185.

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NGC 205
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Title: Herschel and JCMT observations of the early-type dwarf galaxy NGC 205
Authors: I. De Looze, M. Baes, T.J. Parkin, C.D. Wilson, G.J. Bendo, M. Boquien, A. Boselli, A. Cooray, D. Cormier, J. Fritz, F. Galliano, W. Gear, G. Gentile, V. Lebouteillier, S.C. Madden, H. Roussel, M. Sauvage, M.W.L. Smith, L. Spinoglio, J. Verstappen, L. Young

We present Herschel dust continuum, James Clerk Maxwell Telescope CO(3-2) observations and a search for [CII] 158 micron and [OI] 63 micron spectral line emission for the brightest early-type dwarf satellite of Andromeda, NGC 205. While direct gas measurements (Mgas ~ 1.5e+6 solar masses, HI + CO(1-0)) have proven to be inconsistent with theoretical predictions of the current gas reservoir in NGC 205 (> 1e+7 solar masses), we revise the missing interstellar medium mass problem based on new gas mass estimates (CO(3-2), [CII], [OI]) and indirect measurements of the interstellar medium content through dust continuum emission. Based on Herschel observations, covering a wide wavelength range from 70 to 500 micron, we are able to probe the entire dust content in NGC 205 (Mdust ~ 1.1-1.8e+4 solar masses at Tdust ~ 18-22 K) and rule out the presence of a massive cold dust component (Mdust ~ 5e+5 solar masses, Tdust ~ 12 K), which was suggested based on millimetre observations from the inner 18.4 arcsec. Assuming a reasonable gas-to-dust ratio of ~ 400, the dust mass in NGC 205 translates into a gas mass Mgas ~ 4-7e+6 solar masses. The non-detection of [OI] and the low L_[CII]-to-L_CO(1-0) line intensity ratio (~ 1850) imply that the molecular gas phase is well traced by CO molecules in NGC 205. We estimate an atomic gas mass of 1.5e+4 solar masses associated with the [CII] emitting PDR regions in NGC 205. From the partial CO(3-2) map of the northern region in NGC 205, we derive a molecular gas mass of M_H2 ~ 1.3e+5 solar masses.

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Posts: 131433
Date:
Messier 110
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The dwarf elliptical galaxy M110 (aka NGC 205) is a member of the local group of galaxies, and a satellite of the Andromeda spiral galaxy .
M110 is about 2.9 million light years away,and is only about 15,000 light-years across, comparable in size to the Milky Ways the Large and Small Magellanic Clouds.


Credit Johannes Schedler (Panther Observatory)

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