10,711 research outputs found
A SINFONI view of Galaxy Centers: Morphology and Kinematics of five Nuclear Star Formation Rings
We present near-infrared (H- and K-band) integral-field observations of the
circumnuclear star formation rings in five nearby spiral galaxies. The data,
obtained at the Very Large Telescope with the SINFONI spectrograph, are used to
construct maps of various emission lines that reveal the individual star
forming regions ("hot spots") delineating the rings. We derive the
morphological parameters of the rings, and construct velocity fields of the
stars and the emission line gas. We propose a qualitative, but robust,
diagnostic for relative hot spot ages based on the intensity ratios of the
emission lines Brackett gamma, HeI, and [FeII]. Application of this diagnostic
to the data presented here provides tentative support for a scenario in which
star formation in the rings is triggered predominantly at two well-defined
regions close to, and downstream from, the intersection of dust lanes along the
bar with the inner Lindblad resonance.Comment: 45 pages incl. 4 tables and 12 (mostly color) figures. Accepted for
publication in AJ. A version with full resolution figures can be obtained at
ftp://ftp.rssd.esa.int/pub/tboeker/SINFONI/ms.pd
Stellar population synthesis models between 2.5 and 5 {\mu}m based on the empirical IRTF stellar library
We present the first single-burst stellar population models in the infrared
wavelength range between 2.5 and 5 {\mu}m which are exclusively based on
empirical stellar spectra. Our models take as input 180 spectra from the
stellar IRTF (Infrared Telescope Facility) library. Our final single-burst
stellar population models are calculated based on two different sets of
isochrones and various types of initial mass functions of different slopes,
ages larger than 1 Gyr and metallicities between [Fe/H] = -0.70 and 0.26. They
are made available online to the scientific community on the MILES web page. We
analyse the behaviour of the Spitzer [3.6]-[4.5] colour calculated from our
single stellar population models and find only slight dependences on both
metallicity and age. When comparing to the colours of observed early-type
galaxies, we find a good agreement for older, more massive galaxies that
resemble a single-burst population. Younger, less massive and more metal-poor
galaxies show redder colours with respect to our models. This mismatch can be
explained by a more extended star formation history of these galaxies which
includes a metal-poor or/and young population. Moreover, the colours derived
from our models agree very well with most other models available in this
wavelength range. We confirm that the mass-to-light ratio determined in the
Spitzer [3.6] {\mu}m band changes much less as a function of both age and
metallicity than in the optical bands.Comment: 25 pages, 19 figures, published in MNRAS, models can be downloaded
from http://miles.iac.e
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