18 research outputs found
Unveiling the complexity of the X-ray spectra of Seyfert 1 galaxies: an XMM-Newton view
Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 28-09-201
Kinematics of gas and stars in circumnuclear star-forming regions of early type spirals
(Abbr.) We present high resolution (R~20000) spectra in the blue and the far
red of cicumnuclear star-forming regions (CNSFRs) in three early type spirals
(NGC3351, NGC2903 and NGC3310) which have allowed the study of the kinematics
of stars and ionized gas in these structures and, for the first time, the
derivation of their dynamical masses for the first two. In some cases these
regions, about 100 to 150 pc in size, are seen to be composed of several
individual star clusters with sizes between 1.5 and 4.9 pc estimated from
Hubble Space Telescope (HST) images. The stellar dispersions have been obtained
from the Calcium triplet (CaT) lines at 8494,8542,8662 \AA,
while the gas velocity dispersions have been measured by Gaussian fits to the
H and [OIII] 5007 \AA lines on the high dispersion
spectra. Values of the stellar velocity dispersions are between 30 and 68 km/s.
We apply the virial theorem to estimate dynamical masses of the clusters,
assuming that systems are gravitationally bounded and spherically symmetric,
and using previously measured sizes. The measured values of the stellar
velocity dispersions yield dynamical masses of the order of 10 to 10
solar masses for the whole CNSFRs. Stellar and gas velocity dispersions are
found to differ by about 20 to 30 km/s with the H emission lines being
narrower than both the stellar lines and the [OIII] 5007 \AA
lines. The twice ionized oxygen, on the other hand, shows velocity dispersions
comparable to those shown by stars, in some cases, even larger. We have found
indications of the presence of two different kinematical components in the
ionized gas of the regions...Comment: 4 pages, proceeding of the meeting "Young massive star clusters -
Initial conditions and environments", Granada, Spain, 200
Chemical abundances in Seyfert galaxies : VII. Direct abundance determination of neon based on optical and infrared emission lines
For the first time, neon abundance has been derived in the narrow line region from a sample of Seyfert 2 nuclei. In view of this, we compiled from the literature fluxes of optical and infrared (IR) narrow emission lines for 35 Seyfert 2 nuclei in the local universe (z 0.06). The relative intensities of emission lines were used to derive the ionic and total neon and oxygen abundances through electron temperature estimations (Te-method). For the neon, abundance estimates were obtained by using both Te-method and IR-method. Based on photoionization model results, we found a lower electron temperature [te(Ne iii)] for the gas phase where the Ne2 + is located in comparison with t3 for the O2 + ion. We find that the differences (D) between Ne2 +/H+ ionic abundances calculated from IR-method and Te-method (assuming t3 in the Ne2 +/H+ derivation) are similar to the derivations in star-forming regions (SFs) and they are reduced by a mean factor of ∼3 when te(Ne iii) is considered. We propose a semi-empirical Ionization Correction Factor (ICF) for the neon, based on [Ne II]12.81μm, [Ne III]15.56μm, and oxygen ionic abundance ratios. We find that the average Ne/H abundance for the Seyfert 2s sample is nearly 2 times higher than similar estimate for SFs. Finally, for the very high metallicity regime (i.e. [12 + log(O/H) 8.80]) an increase in Ne/O with O/H is found, which likely indicates secondary stellar production for the neon
Chemical abundances in Seyfert galaxies : V. The discovery of shocked emission outside the AGN ionization axis
We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to 30 000 K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle
Precision abundance analysis of bright HII galaxies
We present high signal-to-noise spectrophotometric observations of seven
luminous HII galaxies. The observations have been made with the use of a
double-arm spectrograph which provides spectra with a wide wavelength coverage,
from 3400 to 10400\AA free of second order effects, of exactly the same region
of a given galaxy. These observations are analysed applying a methodology
designed to obtain accurate elemental abundances of oxygen, sulphur, nitrogen,
neon, argon and iron in the ionized gas. Four electron temperatures and one
electron density are derived from the observed forbidden line ratios using the
five-level atom approximation. For our best objects errors of 1% in
t_e([OIII]), 3% in t_e([OII]) and 5% in t_e([SIII]) are achieved with a
resulting accuracy of 7% in total oxygen abundances, O/H.
The ionisation structure of the nebulae can be mapped by the theoretical
oxygen and sulphur ionic ratios, on the one side, and the corresponding
observed emission line ratios, on the other -- the \eta and \eta' plots --. The
combination of both is shown to provide a means to test photo-ionisation model
sequences currently applied to derive elemental abundances in HII galaxies.Comment: 24 pages, 8 figures, accepted by MNRA
The circumnuclear environment of the peculiar galaxy NGC 3310
Gas and star velocity dispersions have been derived for eight circumnuclear
star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC3310
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 fits to the Hb 4861A and [OIII]5007A emission lines.
The CNSFRs stellar velocity dispersions range from 31 to 73 km/s. 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
7.1 x 10 M, for the whole CNSFR between 2 x 10 and 1.4 x 10
M, and 5.3 x 10 M for the nucleus inside the inner 14.2 pc.
The masses of the ionizing stellar population responsible for the HII region
gaseous emission have been derived from their published Ha luminosities and are
found to be between 8.7 x 10 and 2.1 x 10 M for the
star-forming regions, and 2.1 x 10 M for the galaxy nucleus; they
therefore constitute between 1 and 7 per cent of the total dynamical mass.
The ionized gas kinematics is complex; two different kinematical components
seem to be present as evidenced by different line widths and Doppler shifts.Comment: 24 pages, accepted by MNRA
Kinematics of gas and stars in the circumnuclear starforming ring of NGC 3351
We have measured gas and stellar velocity dispersions in 5 circumnuclear
starforming regions (CNSFRs) and the nucleus of the barred spiral galaxy NGC
3351. The stellar dispersions have been obtained from high resolution spectra
of the CaT lines at 8494, 8542, 8662 \AA, while the gas
velocity dispersions have been measured by Gaussian fits to the H
4861 \AA line on high dispersion spectra.
The CNSFRs, with sizes of about 100 to 150 pc in diameter, are seen to be
composed of several individual star clusters with sizes between 1.7 and 4.9 pc
on an HST image. Using the stellar velocity dispersions, we have derived
dynamical masses for the entire starforming complexes and for the individual
star clusters. Values of the stellar velocity dispersions are between 39 and 67
km s. Dynamical masses for the whole CNSFRs are between 4.9
10 and 4.3 10 M and between 1.8 and 8.7
10 M for the individual star clusters.
Stellar and gas velocity dispersions are found to differ by about 20 km
s with the H lines being narrower than both the stellar lines and
the [O{\sc iii}] 5007 \AA lines. We have found indications for the
presence of two different kinematical components in the ionised gas of the
regions. The radial velocity curve shows deviation from circular motions for
the ionised hydrogen consistent with its infall towards the central regions of
the galaxy at a velocity of about 25 km s. 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 S/N in particular for the
O lines.Comment: 17 pages, 13 figures, 7 tables - Accepted by MNRA
On the derivation of dynamical masses of the stellar clusters in the circumnuclear region of NGC2903
(Abridged) Gas and star velocity dispersions have been derived for four
circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral
galaxy NGC2903 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, 8662A, using cross-correlation techniques while gas
velocity dispersions have been measured by Gaussian fits to the Hbeta line.
The CNSFRs, with sizes of about 100 to 150pc in diameter, show a complex
structure at the Hubble Space Telescope resolution, with a good number of
subclusters with linear diameters between 3 and 8pc. Their stellar velocity
dispersions range from 39 to 67 km/s. 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 x 10 M and upper
limits to the masses for the whole CNSFR between 4.9 x 10 and 4.3 x 10
M. ...Comment: 20 pages, 12 figures, 6 tables. Accepted for publication in MNRA
Abundance determination of multiple star-forming regions in the HII galaxy SDSS J165712.75+321141.4
We analyze high signal-to-noise spectrophotometric observations acquired
simultaneously with TWIN, a double-arm spectrograph, from 3400 to 10400 \AA 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 precision, 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 O2+ measured
thermal and ionic structures within the errors in the three knots, with
deviations of only 0.1 dex in the case of O+ and S2+ 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 population 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 parameter
is 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.Comment: 18 pages, 10 figures, accepted by MNRA
Erratum: [Kinematics of gas and stars in the circumnuclear star-forming ring of NGC 3351. Monthly Notices of the Royal Astronomical Society 378 (2007) : 163-178]
This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Hägele, G.F., Díaz, A.I., Cardaci, M.V., Terlevich, E. and R. Terlevich. Erratum: Kinematics of gas and stars in the circumnuclear star-forming ring of NGC 3351. Monthly Notices of the Royal Astronomical Society 385 (2008): 54