1,916 research outputs found
New candidate planetary nebulae in M81
A 34 x 34 arcmin field centred on the spiral galaxy M81 has been searched for
emission-line objects using the prime focus wide field camera (WFC) of the 2.54
m Isaac Newton Telescope (La Palma, Spain). A total of 171 candidate planetary
nebulae (PNe) are found, 54 of which are in common with the ones detected by
Jacoby et al. (1989). The behaviour of PNe excitation as a function of
galactocentric distance is examined, and no significant variations are found.
The PNe luminosity function is built for the disk and bulge of M81, separately.
A distance modulus of 27.92+-0.23 mag is found for disk PNe, in good agreement
with previous distance measurements for M81 (Jacoby et al. 1989; Huterer et al.
1995).Comment: 7 pages including 2 tables. A&A accepted; also available at
http://www.iac.es/publicaciones/preprints.htm
Spectroscopy of planetary nebulae in M33
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
& D'Odorico 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.Comment: 18 pages, 1 JPEG figure and 3 Postscript figures, Accepted for
publication in A&
The S2N2 metallicity calibrator and the abundance gradient of M 33
We introduce the log(Ha/[SII]6717+6731) vs. log(Ha/[NII]6583) (S2N2)
diagnostic diagram as metallicity and ionisation parameter indicator for HII
regions in external galaxies. The location of HII regions in the S2N2 diagram
was studied both empirically and theoretically. We found that, for a wide range
of metallicities, the S2N2 diagram gives single valued results in the
metallicity-ionisation parameter plane. We demonstrate that the S2N2 diagram is
a powerful tool to estimate metallicities of high-redshift (z ~ 2) HII
galaxies. Finally, we derive the metallicity for 76 HII regions in M33 from the
S2N2 diagram and calculate an O/H abundance gradient for this galaxy of -0.05
(+-0.01) dex kpc^-1.Comment: 10 pages, 3 figures and 2 tables. Accepted for publication in MNRA
The population of planetary nebulae and HII regions in M81. A study of radial metallicity gradients and chemical evolution
We analyze the chemical abundances of planetary nebulae and HII regions in
the M81 disk for insight on galactic evolution, and compare it with that of
other galaxies, including the Milky Way. We acquired Hectospec/MMT spectra of
39 PNe and 20 HII regions, with 33 spectra viable for temperature and abundance
analysis. Our PN observations represent the first PN spectra in M81 ever
published, while several HII region spectra have been published before,
although without a direct electron temperature determination. We determine
elemental abundances of helium, nitrogen, oxygen, neon, sulfur, and argon in
PNe and HII regions, and determine their averages and radial gradients. The
average O/H ratio of PNe compared to that of the HII regions indicates a
general oxygen enrichment in M81 in the last ~10 Gyr. The PN metallicity
gradient in the disk of M81 is -0.055+-0.02 dex/kpc. Neon and sulfur in PNe
have a radial distribution similar to that of oxygen, with similar gradient
slopes. If we combine our HII sample with the one in the literature we find a
possible mild evolution of the gradient slope, with results consistent with
gradient steepening with time. Additional spectroscopy is needed to confirm
this trend. There are no Type I PNe in our M81 sample, consistently with the
observation of only the brightest bins of the PNLF, the galaxy metallicity, and
the evolution of post-AGB shells. Both the young and the old populations of M81
disclose shallow but detectable negative radial metallicity gradient, which
could be slightly steeper for the young population, thus not excluding a mild
gradients steepening with the time since galaxy formation. During its evolution
M81 has been producing oxygen; its total oxygen enrichment exceeds that of
other nearby galaxies.Comment: A&A, in pres
Plasma adrenomedullin is associated with short-term mortality and vasopressor requirement in patients admitted with sepsis
Introduction: The incidence of death among patients admitted for severe sepsis or septic shock is high. Adrenomedullin (ADM) plays a central role in initiating the hyperdynamic response during the early stages of sepsis. Pilot studies indicate an association of plasma ADM with the severity of the disease. In the present study we utilized a novel sandwich immunoassay of bioactive plasma ADM in patients hospitalized with sepsis in order to assess the clinical utility.Methods: We enrolled 101 consecutive patients admitted to the emergency department with suspected sepsis in this study. Sepsis was defined by fulfillment of at least two systemic inflammatory response syndrome (SIRS) criteria plus clinical suspicion of infection. Plasma samples for ADM measurement were obtained on admission and for the next four days. The 28-day mortality rate was recorded.Results: ADM at admission was associated with severity of disease (correlation with Acute Physiology and Chronic Health Evaluation II (APACHE II) score: r = 0.46; P <0.0001). ADM was also associated with 28-day mortality (ADM median (IQR): survivors: 50 (31 to 77) pg/mL; non-survivors: 84 (48 to 232) pg/mL; P <0.001) and was independent from and additive to APACHE II (P = 0.02). Cox regression analysis revealed an additive value of serial measurement of ADM over baseline assessment for prediction of 28-day mortality (P < 0.01). ADM was negatively correlated with mean arterial pressure (r = -0.39; P <0.0001), and it strongly discriminated those patients requiring vasopressor therapy from the others (ADM median (IQR): no vasopressors 48 (32 to 75) pg/mL; with vasopressors 129 (83 to 264) pg/mL, P <0.0001).Conclusions: In patients admitted with sepsis, severe sepsis or septic shock plasma ADM is strongly associated with severity of disease, vasopressor requirement and 28-day mortality
Abundances and kinematics for ten anticentre open clusters
Open clusters are distributed all across the disk and are convenient tracers
of its properties. In particular, outer disk clusters bear a key role for the
investigation of the chemical evolution of the Galactic disk. The goal of this
study is to derive homogeneous elemental abundances for a sample of ten outer
disk OCs, and investigate possible links with disk structures such as the
Galactic Anticenter Stellar Structure. We analyse high-resolution spectra of
red giants, obtained from the HIRES@Keck and UVES@VLT archives. We derive
elemental abundances and stellar atmosphere parameters by means of the
classical equivalent width method. We also performed orbit integrations using
proper motions. The Fe abundances we derive trace a shallow negative radial
metallicity gradient of slope -0.027+/-0.007 dex.kpc-1 in the outer 12 kpc of
the disk. The [alpha/Fe] gradient appears flat, with a slope of 0.006+/-0.007
dex.kpc-1 . The two outermost clusters (Be 29 and Sau 1) appear to follow
elliptical orbits. Be 20 also exhibits a peculiar orbit with a large excursion
above the plane. The irregular orbits of the three most metal-poor clusters (of
which two are located at the edge of the Galactic disk), if confirmed by more
robust astrometric measurements such as those of the Gaia mission, are
compatible with an inside-out formation scenario for the Milky Way, in which
extragalactic material is accreted onto the outer disk. We cannot determine if
Be 20, Be 29,and Sau 1 are of extragalactic origin, as they may be old genuine
Galactic clusters whose orbits were perturbed by accretion events or minor
mergers in the past 5 Gyr, or they may be representants of the thick disk
population. The nature of these objects is intriguing and deserves further
investigations in the near future.Comment: 17 pages, 9 figures; accepted for publication in A&
The Local Group Census: planetary nebulae in Sextans B
Five planetary nebulae (PNe) have been discovered in the nearby dwarf
irregular galaxy. Emission line images were obtained using the Wide Field
Camera of the 2.5m Isaac Newton Telescope (INT) at La Palma (Spain). The
candidate PNe were identified by their point-like appearance and relatively
strong [OIII] emission-line fluxes. They are located within a galactocentric
distance of 2.8 arcmin, corresponding to 1.1 kpc at the distance of Sextans B.
Luminosities are in the range 1800--5600Lsolar. Sextans B is one of the
smallest dwarf irregular galaxies with a PN population. The number of PNe
detected suggest an enhanced star formation rate between 1 and 5 Gyr ago.Comment: 7 pages, 2 figure
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