Author: OLGA MERCEDES VEGA CASANOVA
OLGA MERCEDES VEGA CASANOVA (2005)
Poder (Ciencias sociales)
Política y gobierno
OLGA MERCEDES VEGA CASANOVA (2013)
We produce an atlas of homogeneously reduced and calibrated low resolution IRS spectra of the nuclear regions of nearby early-type galaxies (i.e. Es and S0s, ETGs), in order to build a reference sample in the mid-infrared window. From the Spitzer Heritage Archive we extract ETGs in the Revised Shapley-Ames Catalog of Bright Galaxies having an IRS SL and/or LL spectrum. We recover 91 spectra out of 363 galaxies classified as ETGs in the catalog: 56 E (E0-E6), 8 mixed E/S0+S0/E, 27 S0 (both normal and barred - SB0) plus mixed types SB0/Sa+SB0/SBa. For each galaxy, we provide the fully reduced and calibrated spectrum, the intensity of nebular and molecular emission lines as well as of the Polycyclic Aromatic Hydrocarbons (PAHs) after a template spectrum of a passively evolving ETG has been subtracted. Spectra are classified into five mid-infrared classes, ranging from AGN (class-4) and star forming nuclei (class-3), transition class-2 (with PAHs) and class-1 (no-PAHs) to passively evolving nuclei (class-0). A demographic study of mid-infrared spectra shows that Es are significantly more passive than S0s:46⁺¹¹₋₁₀% of Es and 20⁺¹¹₋₇ % of S0s have a spectrum of class-0. Emission lines are revealed in 64⁺¹²₋₆ % of ETGs. The H₂S(1) line is found with similar rate in Es (34⁺¹⁰₋₈ %) and in S0s (51⁺¹⁵₋₁₂%). PAHs are detected in 47⁺⁸₋₇% of ETGs, but only 9⁺⁴₋₃% have PAHs ratios typical of star forming galaxies. Several indicators, such as peculiar morphologies and kinematics, dust–lane irregular shape, radio and X-ray properties, suggest that mid-infrared spectral classes are connected to phases of accretion/feedback phenomena occurring in the nuclei of ETGs.
Infrared: galaxies Galaxies: elliptical and lenticular, cD Galaxies: fundamental parameters Techniques: spectroscopic CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA
We analyse the photometric, chemical, star formation history and structural properties of the brightest globular cluster (GC) in M81, referred as GC1 in this work, with the intention of establishing its nature and origin. We find that it is a metal-rich ([Fe/H]=−0.60 ± 0.10), alpha-enhanced ([α/Fe] ~ 0.20 ± 0.05), core-collapsed (core radius rc = 1.2 pc, tidal radius rt = 76rc), old (> 13 Gyr) cluster. It has an ultraviolet excess equivalent of ~ 2500 blue horizontal branch stars. It is detected in X-rays indicative of the presence of low-mass binaries. With a mass of 1.0 × 10⁷ Mʘ, the cluster is comparable in mass to M31-G1 and is four times more massive than ω Cen. The values of rc, absolute magnitude and mean surface brightness of GC1 suggest that it could be, like massive GCs in other giant galaxies, the left-over nucleus of a dissolved dwarf galaxy.
Catalogs Galaxies: individual (M81) Galaxies: spiral Galaxies: star clusters Globular clusters: general CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA