Spectroscopy and V,I CCD photometry of the dwarf irregular galaxy SBS 1129+576 are presented for the first time. The CCD images reveal a chain of compact H II regions within the elongated ...low-surface-brightness (LSB) component of the galaxy. Star formation takes place mainly in two high-surface-brightness H II regions. The mean (V-I) colour of the LSB component in the surface brightness interval between 23 and 26 mag/sq.arcsec is relatively blue ~0.56+/-0.03 mag, as compared to the (V-I)~0.9-1.0 for the majority of known dwarf irregular and blue compact dwarf (BCD) galaxies. Spectroscopy shows that the galaxy is among the most metal-deficient galaxies with an oxygen abundance 12+log(O/H)= 7.36+/-0.10 in the brightest H II region and 7.48+/-0.12 in the second brightest H II region, or 1/36 and 1/28 of the solar value, respectively. Hbeta and Halpha emission lines and Hdelta and Hgamma absorption lines are detected in a large part of the LSB component. We use two extinction-insensitive methods based on the equivalent widths of (1) emission and (2) absorption Balmer lines to put constraints on the age of the stellar populations in the galaxy. In addition, we use two extinction-dependent methods based on (3) the spectral energy distribution (SED) and (4) the (V-I) colour. The observed properties of the LSB component can be reproduced by a stellar population forming continuously since 10 Gyr ago, provided that the star formation rate has increased during the last 100 Myr by a factor of 6 to 50 and no extinction is present. However, the observational properties of the LSB component can be reproduced equally well by continuous star formation which started not earlier than 100 Myr ago and stopped at 5 Myr, if some extinction is assumed.(Abridged)
We present a detailed optical spectroscopic and B,V,I,Halpha photometric study of the metal-deficient cometary blue compact dwarf (BCD) galaxy SBS 1415+437. We derive an oxygen abundance ...12+log(O/H)=7.61+/-0.01 and 7.62+/-0.03 (Z =Zsun/20) in the two brightest H II regions, among the lowest in BCDs. The helium mass fractions in these regions are Y=0.246+/-0.003 and 0.243+/-0.010. Four techniques based on the equivalent widths of the hydrogen emission and absorption lines, the spectral energy distribution and the colours of the galaxy are used to put constraints on the age of the stellar population in the low-surface-brightness (LSB) component of the galaxy, assuming two limiting cases of star formation (SF), the case of an instantaneous burst and that of a continuous SF with a constant or a variable star formation rate (SFR). The spectroscopic and photometric data for different regions of the LSB component are well reproduced by a young stellar population with an age t<250 Myr, assuming a small extinction in the range A(V)= 0-0.6 mag. Assuming no extinction, we find that the upper limit for the mass of the old stellar population, formed between 2.5 Gyr and 10 Gyr, is not greater than ~(1/20 - 1) of that of the stellar population formed during the last ~250 Myr. Depending on the region considered, this also implies that the SFR in the most recent SF period must be 20 to 1000 times greater than the SFR at ages > 2.5 Gyr. We compare the photometric and spectroscopic properties of SBS 1415+437 with those of a sample of 26 low-metallicity dwarf irregular and BCD galaxies. We show that there is a clear trend for the stellar LSB component of lower-metallicity galaxies to be bluer. This trend cannot be explained only by metallicity effects. There must be also a change in the age of the stellar populations.
We present broad-band V and I imaging and long-slit spectroscopy in the optical range 3600-7500A of the dwarf irregular galaxy HS 1442+4250. The oxygen abundance 12+log(O/H)=7.63+/-0.02 (Z=Zsun/19) ...in the brightest H II region of HS 1442+4250 places the galaxy among the most metal-deficient emission-line galaxies. The low metallicity and blue colour (V-I)~0.4 mag of the low-surface-brightness (LSB) component make HS 1442+4250 a likely rare young dwarf galaxy candidate. We use four methods to estimate the stellar population age in the LSB component of HS 1442+4250. Different star formation histories are considered. The equivalent widths of hydrogen Halpha and Hbeta emission lines, and of hydrogen Hgamma and Hdelta absorption lines, the spectral energy distribution and the observed (V-I) colours of the LSB regions are reproduced quite well by models with only young and intermediate-age stellar populations. By contrast, the observational data cannot be reproduced by a stellar population formed continuously with a constant star formation rate in the age range from 0 to > 2 Gyr. While a faint old stellar population in HS 1442+4250 with an age > 2 Gyr is not excluded, we find no evidence for such a population from the present data.
We present the quantitative rest-frame B morphological evolution and galaxy merger fractions at 0.2 < z < 1.2 as observed by the All-wavelength Extended Groth Strip International Survey (AEGIS). We ...use the Gini coefficent and M_20 to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0.4 L_B^*, assuming pure luminosity evolution of 1.3 M_B per unit redshift. We find that the merger fraction remains roughly constant at 10 +/- 2% for 0.2 < z < 1.2. The fraction of E/S0/Sa increases from 21+/- 3% at z ~ 1.1 to 44 +/- 9% at z ~ 0.3, while the fraction of Sb-Ir decreases from 64 +/- 6% at z ~ 1.1 to 47 +/- 9% at z ~ 0.3. The majority of z < 1.2 Spitzer MIPS 24 micron sources with L(IR) > 10^11 L_sun are disk galaxies, and only ~ 15% are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z ~ 1.1, while E/S0/Sa makeup over 90% of the red sequence at z ~ 0.3. Approximately 2% of our full sample are red mergers. We conclude (1) the galaxy merger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease in the volume-averaged star-formation rate density since z ~ 1 is a result of declining star-formation in disk galaxies rather than a disappearing population of major mergers; (3) the build-up of the red sequence at z < 1 can be explained by a doubling in the number of spheroidal galaxies since z ~ 1.2.
As part of the "All Wavelength Extended Groth Strip International Survey" (AEGIS), we describe the panchromatic characterization of an X-ray luminous active galactic nucleus (AGN) in a merging galaxy ...at z=1.15. This object is detected at infrared (8mic, 24mic, 70mic, 160mic), submillimeter (850mic) and radio wavelengths, from which we derive a bolometric luminosity L_bol ~ 9x10^12 Lsol. We find that the AGN clearly dominates the hot dust emission below 40mic but its total energetic power inferred from the hard X-rays is substantially less than the bolometric output of the system. About 50% of the infrared luminosity is indeed produced by a cold dust component that probably originates from enshrouded star formation in the host galaxy. In the context of a coeval growth of stellar bulges and massive black holes, this source might represent a ``transition'' object sharing properties with both quasars and luminous starbursts. Study of such composite galaxies will help address how the star formation and disk-accretion phenomena may have regulated each other at high redshift and how this coordination may have participated to the build-up of the relationship observed locally between the masses of black holes and stellar spheroids.
In this the first of a series of Letters, we present a description of the panchromatic data sets that have been acquired in the Extended Groth Strip region of the sky. Our survey, the All-wavelength ...Extended Groth strip International Survey (AEGIS), is intended to study the physical properties and evolutionary processes of galaxies at z ~ 1. It includes the following deep, wide-field imaging data sets: Chandra/ACIS X-ray (0.5 - 10 keV), GALEX ultraviolet (1200 - 2500 Angstrom), CFHT/MegaCam Legacy Survey optical (3600 - 9000 Angstroms), CFHT/CFH12K optical (4500 - 9000 Angstroms), Hubble Space Telescope/ACS optical (4400 - 8500 Angstroms), Palomar/WIRC near-infrared (1.2 - 2.2 microns), Spitzer/IRAC mid-infrared (3.6 - 8.0 microns), Spitzer/MIPS far-infrared (24 - 70 microns), and VLA radio continuum (6 - 20 cm). In addition, this region of the sky has been targeted for extensive spectroscopy using the DEIMOS spectrograph on the Keck II 10 m telescope. Our survey is compared to other large multiwavelength surveys in terms of depth and sky coverage.
Sialolipom der Glandula parotis Fritzsche, F.R.; Bode, P.K.; Stinn, B. ...
Der Pathologe,
2009/11, Letnik:
30, Številka:
6
Journal Article
Zusammenfassung
Das Sialolipom ist eine relativ neue und seltene Lipomvariante der Speicheldrüsen, welche durch die Kombination von klassischer Lipommorphologie mit nichtneoplastischen ...duktuloazinären Speicheldrüsenanteilen gekennzeichnet ist. Inklusive des vorliegenden Falles wurden bislang 27 Sialolipome publiziert, davon 14 in der Glandula parotis. Wir beschreiben die klinischen, radiologischen und pathomorphologischen Eigenschaften eines Sialolipoms der Ohrspeicheldrüse bei einem 43 Jahre alten Patienten.
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