Mónica V. Cardaci

Kinematics of gas and stars in the circumnuclear star-forming ring of NGC 3351

We have measured gas and stellar velocity dispersions in five circumnuclear star-forming regions (CNSFRs) and the nucleus of the barred spiral galaxy NGC 3351. The stellar dispersions have been obtained from high-resolution spectra of the Ca II triplet (CaT) lines at λλ8494, 8542, 8662 A, while the gas velocity dispersions have been measured by Gaussian fits to the Hβ λ4861 A line on high-dispersion spectra. The CNSFRs, with sizes of about 100 to 150pc in diameter, are seen to be composed of several individual star clusters with sizes between 1.7 and 4.9 pc on a Hubble Space Telescope (HST) image. Using the stellar velocity dispersions, we have derived dynamical masses for the entire star-forming complexes and for the individual star clusters. Values of the stellar velocity dispersions are between 39 and 67 km s -1 . Dynamical masses for the whole CNSFRs are between 4.9 x 106 and 4.3 x 10 7 M ⊙ and between 1.8 and 8.7 x 10 6 M ⊙ for the individual star clusters. Stellar and gas velocity dispersions are found to differ by about 20kms -1 with the Hβ lines being narrower than both the stellar lines and the [O III]λ5007 A lines. We have found indications for the presence of two different kinematical components in the ionized gas of the regions. The radial velocity curve shows deviation from circular motions for the ionized hydrogen consistent with its infall towards the central regions of the galaxy at a velocity of about 25 km s -1 . To disentangle the origin of these two components it will be necessary to map these regions with high spectral and spatial resolution and much better signal-to-noise ratio in particular for the O 2+ lines.

An X-ray look at the Seyfert 1 Galaxy Mrk 590: XMM-Newton and Chandra reveal complexity in circumnuclear gas

Context. This paper reports on a partially simultaneous observation of the bright Seyfert 1 Galaxy Mrk 590, performed by XMM-Newton and Chandra. Aims. The long exposure (∼100 ks) allows us to investigate the Fe K complex at 6−7 keV and the presence of soft X-ray spectral features in great detail. Methods. We have analysed XMM-Newton data from the European Photon Imaging Camera (EPIC) in the 0.5−12 keV band and from the Reflection Grating Spectrometer (RGS) in the 0.35−2.5 keV band, and data from the High Energy Transmission Gratings (HETGs) onboard Chandra. UV and optical data from the Optical Monitor (OM) onboard XMM-Newton are also included in the analysis. Results. The broad band spectrum is well described by an unabsorbed power law and three unresolved Fe K lines in the 6− 7k eV range. The presence of a Compton reflection component and a narrow Fe K line at 6.4 keV is consistent with an origin via torus reflection. The ionised Fe lines at ∼6.7 and 7 keV are instead most likely originated by scattering on a warm and ionised gas. The soft X-ray spectrum appears to be almost featureless due to the very bright continuum emission, except for one emission line identified as OVIII Lyα detected at ∼19 A by both RGS and Chandra-MEG. The emerging picture consists of an active nucleus seen directly on a “clean” line of sight without intervening material, surrounded by photoionised circumnuclear gas at a high ionisation level. We also study three serendipitous sources in the field of view of Chandra and XMM-Newton. One of these sources may be identified with an ULX of L0.3−10 keV ∼ 4 × 10 40 erg/s.

The circumnuclear environment of the peculiar galaxy NGC 3310

Gas and star velocity dispersions have been derived for eight circumnuclear starforming regions (CNSFRs) and the nucleus of the spiral galaxy NGC 3310 using high resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the Caii triplet in the near-IR, using cross-correlation techniques, while gas velocity dispersions have been measured by Gaussian ts to the H

On the derivation of dynamical masses of the stellar clusters in the circumnuclear region of NGC 2903

Gas and star velocity dispersions have been derived for four circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC 2903 using high resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet (CaT) lines at 8494, 8542, 8662 A, using cross-correlation techniques while gas velocity dispersions have been measured by Gaussian ts to the H 4861 A line. The CNSFRs, with sizes of about 100 to 150 pc in diameter, show a complex structure at the Hubble Space Telescope (HST) resolution, with a good number of subclusters with linear diameters between 3 and 8 pc. Their stellar velocity dispersions range from 39 to 67 km s 1 . These values, together with the sizes measured on archival HST images yield upper limits to the dynamical masses for the individual star clusters between 1.8 and 8.7 10 6 M and upper limits to the masses for the whole CNSFR between 4.9 10 6 and 4.3 10 7 M . The masses of the ionizing stellar population responsible for the Hii region gaseous emission have been derived from their published H luminosities and are found to be between 1.9 and 2.5 10 6 M for the star-forming regions, and 2.1 10 5 M for the galaxy nucleus therefore constituting between 1 and 4 per cent of the total dynamical mass. In the CNSFR star and gas velocity dispersions are found to dier

Abundance determination of multiple star-forming regions in the H II galaxy SDSS J165712.75+321141.4

We analyze high signal-to-noise spectrophotometric observations acquired simul- taneously with TWIN, a double-arm spectrograph, from 3400 to 10400u of three star-forming regions in the Hii galaxy SDSS J165712.75+321141.4. We have measured four line temperatures: Te((Oiii)), Te((Siii)), Te((Oii)), and Te((Sii)), with high preci- sion, rms errors of order 2%, 5%, 6% and 6%, respectively, for the brightest region, and slightly worse for the other two. The temperature measurements allowed the direct derivation of ionic abundances of oxygen, sulphur, nitrogen, neon and argon. We have computed CLOUDY tailor-made models which reproduce the O 2+ mea- sured thermal and ionic structures within the errors in the three knots, with deviations of only 0.1 dex in the case of O + and S 2+ ionic abundances. In the case of the electron temperature and the ionic abundances of S + /H + , we find major discrepancies which could be consequence of the presence of colder diffuse gas. The star formation history derived using STARLIGHT shows a similar age distribution of the ionizing popula- tion among the three star-forming regions. This fact suggests a similar evolutionary history which is probably related to a process of interaction with a companion galaxy that triggered the star formation in the different regions almost at the same time. The hardness of the radiation field mapped through the use of the softness parame- teris the same within the observational errors for all three regions, implying that the equivalent effective temperature of the radiation fields are very similar for all the studied regions of the galaxy, in spite of some small differences in the ionization state of different elements. Regarding the kinematics of the galaxy, the gas rotation curve shows a deviation from the circular motion probably due either to an interaction process or related to an expanding bubble or shell of ionized gas approaching us. A dynamical mass of 2.5×10 10 Mis derived from the rotation curve.

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

This is an electronic version of an article published in Astronomy and Astrophysics. Cardaci, M.V., Santos-Lleo, M., Krongold, Y., Hagele, G.F., Diaz, A.I. and P. Rodriguez-Pascual. Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data. Astronomy and Astrophysics 505 (2009): 541-551

A comprehensive approach to analyzing the XMM-Newton data of Seyfert 1 galaxies

Aims. We seek a comprehensive analysis of all the information provided by the XMM-Newton satellite of the four Seyfert 1 galaxies ESO 359-G19, HE 1143-1810, CTS A08.12, and Mrk 110, including the UV range, to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus. Methods. The continuum emission was studied through the EPIC spectra by taking advantage of the spectral range of these cameras. The high-resolution RGS spectra were analyzed to characterize the absorbing and emission line features that arise in the spectra of the sources. All these data, complemented by information in the UV, are analyzed jointly in order to achieve a consistent characterization of the observed features in each object. Results. The continuum emission of the sources can be characterized either by a combination of a power law and a black body for the weakest objects or by two power law components for the brightest ones. The continuum is not absorbed by neutral or ionized material in the line of sight to any of these sources. In all of them we have identified a narrow Fe-Kα line at 6.4 keV. In ESO 359-G19 we also find an Fexxvi line at about 7 keV. In the soft X-rays band, we identify only one Ovii line in the spectra of HE 1143-1810 and CTS A08.12, and two Ovii-Heα triplets and a narrow Oviii-Lyα emission line in Mrk 110. Conclusions. Not detecting warm material in the line of sight to the low state objects is due to intrinsically weaker or absent absorption in the line of sight and not to a low signal-to-noise ratio in the data. Besides this, the absence of clear emission lines cannot be fully attributed to dilution of those lines by a strong continuum.

Implications of the kinematical structure of circumnuclear star-forming regions on their derived properties

Fil: Hagele, Guillermo Federico. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico la Plata. Instituto de Astrofisica de la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronomicas y Geofisicas; Argentina. Universidad Autonoma de Madrid; Espana

Subarcsecond radio continuum mapping in and around the spiral galaxy NGC 3351 using MERLIN

We report sub-arcsecond scale radio continuum observations of a eld of 35 by 22 arcmin centred in NGC 3351 obtained with the Multi-Element Radio Linked Interferometer Network (MERLIN). We found 23 radio sources in this eld, 6 of which are projected within the D25 isophote of the galaxy, and 3 are located inside the central 100 arcsec in radius. Two of these three are signicantly extended, while the third one is relatively compact. This one is the only source with a previously detected counterpart at other wavelengths and could constitute the radio counterpart of a young supernova remnant. The other two are probably related to jets from a background AGN. We are not able to detect individual supernovae or SNRs in the central region (r < 600 pc) of the galaxy. This could imply that the ionising populations of the circumnuclear star-forming regions (CNSFRs) are too young (less than a few Myr) to host supernovae. Also the diusion length of the relativistic electrons in the ISM associated with the SN from previous events of star formation seems to be larger than our maximum resolution of 50 pc in radius. Detecting the thermal bremsstrahlung emission from the circumnuclear Hii regions probably requires deeper observations.

An XMM-Newton view of a small sample of Seyfert, 1 Galaxies

We present a detailed analysis of all the X-ray data taken by the XMM-Newton satellite of a small sample of five Seyfert 1 galaxies: ESO 359-G19, HE 1143-1810, CTS A08.12, Mkn 110, and UGC 11763. Our aim is to characterize the different components of the material that print the absorption and emission features in the X-ray spectra of these objects. The continuum emission was studied through the EPIC spectra taking advantage of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of these sources.