Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA deep narrowband survey for planetary nebulae at the outskirts of M33
88
0
0.0
(
0
)
Added by
Rebeca Galera-Rosillo Mrs.
Publication date
2017
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
Context: Planetary nebulae (PNe) are excellent tracers of stellar populations with low surface brightness, and therefore provide a powerful method to detect and explore the rich system of substructures discovered around the main spiral galaxies of the Local Group. Aims: We searched the outskirts of the Local Group spiral galaxy M33 (the Triangulum) for PNe to gain new insights into the extended stellar substructure on the northern side of the disc and to study the existence of a faint classical halo. Methods: The search is based on wide field imaging covering a 4.5 square degree area out to a maximum projected distance of about 40 kpc from the centre of the galaxy. The PN candidates are detected by the combination of images obtained in narrowband filters selecting the [OIII]$lambda5007AA$ and H$alpha$ + [NII] nebular lines and in the continuum g and r broadband filters. Results:Inside the bright optical disc of M33, eight new PN candidates were identified, three of which were spectroscopically confirmed. No PN candidates were found outside the limits of the disc. Fourteen additional sources showing [OIII] excess were also discovered. Conclusions:The absence of bright PN candidates in the area outside the galaxy disc covered by this survey sets an upper limit to the luminosity of the underlying population of $mathrm{sim1.6cdot10^{7}L_{odot}}$, suggesting the lack of a massive classical halo, which is in agreement with the results obtained using the RGB population.
rate research
Read More
Near-infrared imaging in the 1 - 0 S(1) emission line of molecular hydrogen is able to detect planetary nebulae (PNe) that are hidden from optical emission line surveys. We present images of 307 objects from the UWISH2 survey of the northern Galactic Plane, and with the aid of mid-infrared colour diagnostics draw up a list of 291 PN candidates. The majority, 183, are new detections and 85 per cent of these are not present in H$alpha$ surveys of the region. We find that more than half (54 per cent) of objects have a bipolar morphology and that some objects previously considered as elliptical or point-source in H$alpha$ imaging, appear bipolar in UWISH2 images. By considering a small subset of objects for which physical radii are available from the H$alpha$ surface brightness-radius relation, we find evidence that the H2 surface brightness remains roughly constant over a factor 20 range of radii from 0.03 to 0.6 pc, encompassing most of the visible lifetime of a PN. This leads to the H$alpha$ surface brightness becoming comparable to that of H2 at large radius (> 0:5 pc). By combining the number of UWISH2 PNe without H$alpha$ detection with an estimate of the PN detection efficiency in H2 emission, we estimate that PN numbers from H$alpha$ surveys may underestimate the true PN number by a factor between 1.5 and 2.5 within the UWISH2 survey area.
Spectroscopic observations of 48 emission-line objects of M33 have been obtained with the multi-object, wide field, fibre spectrograph AF2/WYFFOS at the 4.2m WHT telescope (La Palma, Spain). Line intensities and logarithmic extinction, cbeta, are presented for 42 objects. Their location in the Sabbadin & DOdorico diagnostic diagram (Halpha/[SII] vs Hlapha/[NII]) suggests that >70% of the candidates are Planetary Nebulae (PNe). Chemical abundances and nebular physical parameters have been derived for the three of the six PNe where the 4363A [OIII] emission line was measurable. These are disc PNe, located within a galactocentric distance of 4.1 kpc, and, to date, they are the farthest PNe with a direct chemical abundance determination. No discrepancy in the Helium, Oxygen and Argon abundances has been found in comparison with corresponding abundances of PNe in our Galaxy. Only a lower limit to the sulphur abundance has been obtained since we could not detect any [SIII] line. N/H appears to be lower than the Galactic value; some possible explanations for this under-abundance are discussed.
We report the results of a survey of 442 planetary nebulae at 30 GHz. The purpose of the survey is to develop a list of planetary nebulae as calibration sources which could be used for high frequency calibration in future. For 41 PNe with sufficient data, we test the emission mechanisms in order to evaluate whether or not spinning dust plays an important role in their spectra at 30 GHz. The 30-GHz data were obtained with a twin-beam differencing radiometer, OCRA-p, which is in operation on the Torun 32-m telescope. Sources were scanned both in right ascension and declination. We estimated flux densities at 30 GHz using a free-free emission model and compared it with our data. The primary result is a catalogue containing the flux densities of 93 planetary nebulae at 30 GHz. Sources with sufficient data were compared with a spectral model of free-free emission. The model shows that free-free emission can generally explain the observed flux densities at 30 GHz thus no other emission mechanism is needed to account for the high frequency spectra.
Using spectroscopic data presented in Magrini et al. (2003), we have analyzed with the photoionization code CLOUDY 94.00 (Ferland et al. 1998) 11 Planetary Nebulae belonging to the spiral galaxy M 33. Central star temperatures and nebular parameters have been determined. In particular the chemical abundances of He/H, O/H, N/H, Ar/H, and S/H have been measured and compared with values obtained via the Ionization Correction Factors (ICFs) method, when available. Chemical abundance relationships have been investigated; in particular, a correlation between N/H and N/O similar to the Galactic one (Henry 1989), and a feeble anti-correlation between O/H and N/O have been found. A gradient in O/H across the disc of M~33 is indicatively consistent with the one found from HII regions in this galaxy (Vilchez et al 1988). Further studies in the more external parts of M~33 are however needed to ascertain this point. The present result shows that oxygen and helium abundances (with lower accuracy also nitrogen, argon and sulphur) can be actually estimated from the brightest PNe of a galaxy, even if the electron temperature cannot be measured. We also found that the oxygen abundance is quite independent of the absolute magnitude of the PN and consequently the brightest PNe are representative of the whole PN population. This represents an important tool to measure the metallicity of galaxies at the time of the formation of PNe progenitors.
The age-velocity dispersion relation is an important tool to understand the evolution of the disc of the Andromeda galaxy (M31) in comparison with the Milky Way. We use Planetary Nebulae (PNe) to obtain the age-velocity dispersion relation in different radial bins of the M31 disc. We separate the observed PNe sample based on their extinction values into two distinct age populations. The observed velocities of our high- and low-extinction PNe, which correspond to higher and lower mass progenitors respectively, are fitted in de-projected elliptical bins to obtain their rotational velocities, $V_{phi}$, and corresponding dispersions, $rmsigma_{phi}$. We assign ages to the two PNe populations by comparing central-star properties of an archival sub-sample of PNe, having models fitted to their observed spectral features, to stellar evolution tracks. For the high- and low-extinction PNe, we find ages of $sim2.5$ Gyr and $sim4.5$ Gyr respectively, with distinct kinematics beyond a deprojected radius R$rm_{GC}= 14$ kpc. At R$rm_{GC}$=17--20 kpc, which is the equivalent distance in disc scale lengths of the Sun in the Milky Way disc, we obtain $rmsigma_{phi,~2.5~Gyr}= 61pm 14$ km s$^{-1}$ and $rmsigma_{phi,~4.5~Gyr}= 101pm 13$ km s$^{-1}$. The age-velocity dispersion relation for the M31 disc is obtained in two radial bins, R$rm_{GC}$=14--17 and 17--20 kpc. The high- and low-extinction PNe are associated with the young thin and old thicker disc of M31 respectively, whose velocity dispersion values increase with age. These values are almost twice and thrice that of the Milky Way disc stellar population of corresponding ages. From comparison with simulations of merging galaxies, we find that the age-velocity dispersion relation in the M31 disc measured using PNe is indicative of a single major merger that occurred 2.5 -- 4.5 Gyr ago with an estimated merger mass ratio $approx$ 1:5.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
