arXiv subjects

M. Persic

Publications and source records attributed to M. Persic.

61 records · Page 4Linked to original sources

arXiv1999

Diffuse Thermal Emission from Very Hot Gas in Starburst Galaxies: Spatial Results

New BeppoSAX observations of the nearby prototypical starburst galaxies NGC 253 and M82 are presented. A companion paper (Cappi et al. 1998;astro-ph/9809325) shows that the hard (2-10 keV) spectrum of both galaxies, extracted from the source central regions, is best described by a thermal emission model with kT ~ 6-9 keV and abundances ~ 0.1-0.3 solar. The spatial analysis yields clear evidence that this emission is extended in NGC 253, and possibly also in M82. This quite clearly rules out a LLAGN as the main responsible for their hard X-ray emission. Significant contribution from point-sources (i.e. X-ray binaries (XRBs) and Supernovae Remnants (SNRs)) cannot be excluded; neither can we at present reliably estimate the level of Compton emission. However, we argue that such contributions shouldn't affect our main conclusion, i.e., that the BeppoSAX results show, altogether, compelling evidence for the existence of a very hot, metal-poor interstellar plasma in both galaxies.

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arXiv1998

Dark matter in early-type spiral galaxies: the case of NGC 2179 and of NGC 2775

We present stellar and ionized-gas velocity curves and velocity dispersion profiles for the Sa galaxies NGC 2179 and NGC 2775. Using their luminosity profiles and modeling both their stellar and gaseous kinematics, we have derived the mass distribution of the dark and the luminous matter. This unambiguously shows that, inside one disk length-scale R_D, the stellar bulge and disk account for the whole gravitating mass. The dark matter halo, likely present also at inner radii, becomes an important mass component only for R > 2 R_D. Giving the quantity and quality of the data, our results on these two luminous galaxies serve as strong counter-example to the recent claim according to which also high-luminosity spirals are dark matter dominated at essentially all radii.

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arXiv1998

Diffuse Thermal Emission from Very Hot Gas in Starburst Galaxies: Spectral Results

New BeppoSAX observations of the nearby archetypical starburst galaxies (SBGs) NGC253 and M82 are presented. The main observational result is the unambiguous evidence that the hard (2-10 keV) component is (mostly) produced in both galaxies by thermal emission from a metal-poor (~ 0.1-0.3 solar), hot (kT \~ 6- 9 keV) and extended (see companion paper: Cappi et al. 1998) plasma. Possible origins of this newly discovered component are briefly discussed. A remarkable similarity with the (Milky Way) Galactic Ridge's X-ray emission suggests, nevertheless, a common physical mechanism.

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arXiv1998

BeppoSAX detection of the Fe K line in the nearby starburst galaxy NGC 253

We present BeppoSAX results on the nearby starburst galaxy NGC 253. Although extended, a large fraction of the X-ray emission comes from the nuclear region. Preliminary analysis of the LECS/MECS/PDS ~0.2-60 keV data from the central 4' region indicates that the continuum is well fitted by two thermal models: a ``soft'' component with kT ~ 0.9 keV, and a ``hard'' component with kT ~ 6 keV absorbed by a column density of ~ 1.2 x10**22 cm-2. For the first time in this object, the Fe K line at 6.7 keV is detected, with an equivalent width of ~ 300 eV. This detection, together with the shape of the 2--60 keV continuum, implies that most of the hard X-ray emission is thermal in origin, and constrains the iron abundances of this component to be ~0.25 of solar. Other lines clearly detected are Si, S and Fe L/Ne, in agreement with previous ASCA results. We discuss our results in the context of the starburst-driven galactic superwind model.

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arXiv1998

BeppoSAX detection of the Fe K line in the starburst galaxy NGC253

Preliminary results obtained from BeppoSAX observation of the starburst galaxy NGC253 are presented. X-ray emission from the object is clearly extended but most of the emission is concentrated on the optical nucleus. Preliminary analysis of the LECS and MECS data obtained using the central 4' region indicates that the continuum is well fitted by two thermal components at 0.9 keV and 7 keV. Fe K line at 6.7 keV is detected for the first time in this galaxy; the line has an equivalent width of ~300eV. The line energy and the shape of the 2-10 keV continuum strongly support thermal origin of the hard X-ray emission of NGC253. From the measurement of the Fe K line the abundances can be unambiguously constrained to ~0.25 the solar value. Other lines clearly detected are Si, S and Fe XVIII/Ne, in agreement with ASCA results.

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arXiv1995

A physical distance indicator for spiral galaxies

In this paper we derive a Tully Fisher relation from measured I band photometry and H$α$ rotation curves of a large survey of southern sky spiral galaxies, obtained in Persic \& Salucci (1995) by deprojecting and folding the raw H$α$ data of Mathewson, Ford \& Buchhorn (1992). We calibrate the relation by combining several of the largest clusters in the survey, using an iterative maximum likelihood procedure to account for observational selection effects and Malmquist bias. We also incorporate a simple model for the line of sight depth of each cluster. Our results indicate a Tully Fisher relation of intrinsic dispersion $\sim0.3$ mag, corresponding to a distance error dispersion of $13\%$. Application of this relation to mapping the large scale velocity field is underway.

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arXiv1993

A Unique Mass Function from Galaxies to Clusters ?

We present an observational mass function ranging from galaxies to massive galaxy clusters, derived from direct dynamical mass estimates. Our mass function shows, in the low-mass range of galaxies and groups, a behaviour in agreement with that of standard CDM (n=-2), while in the high-mass range (clusters) our mass function is shallower (and thus contains more power) than standard CDM; it also results shallower than the recent mass function by Bahcall & Cen (1993, ApJ 407, L49).

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