arXiv subjects

S. Arribas

Publications and source records attributed to S. Arribas.

81 records · Page 5Linked to original sources

arXiv2003

INTEGRAL Spectroscopy of IRAS 17208-0014: Implications for the Evolutionary Scenarios of Ultraluminous Infrared Galaxies

New integral field optical fiber spectroscopy obtained with the INTEGRAL system, together with archival {\it {\it HST}} WFPC2 and NICMOS images, have been used to investigate the ultraluminous infrared galaxy IRAS 17208$-$0014, one of the coldest and most luminous objects in the IRAS 1 Jy sample. The 2D gas velocity field identifies the {\it optically faint} K-band nucleus as the {\it true} dynamical nucleus of the galaxy, and shows that the 3 kpc, tilted (i $\sim$ 35 degree) disk is rotating at $Δ$Vsin$i$= 250 km s$^{-1}$. The kinematical, morphological and photometric evidence presented here supports the idea that in IRAS 17208-0014 we are witnessing a luminous, cool ULIRG which is at the final coalescence phase of a system composed of two spirals with m $\leq$ m$^*$, a mass ratio of 2:1, each consisting of a disk+bulge internal structure, that have been involved in a prograde encounter. This system will most likely evolve into an intermediate-mass ($\sim$ L$^*$) elliptical. The multifrequency empirical evidence gathered so far shows no trace of a luminous QSO, and indicates that starbursts dominate the energy output in this galaxy. Therefore IRAS 17208$-$0014 questions the universality of the ULIRG to QSO evolutionary scenario proposed by Sanders and collaborators, and supports the one recently proposed by Colina et al, where two low mass disk galaxies would produce luminous cool ULIRGs that would not evolve into a QSO phase. (abridge)

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arXiv2003

Chandra Observations of Extended X-ray Emission in Arp 220

We resolve the extended X-ray emission from the prototypical ultraluminous infrared galaxy Arp 220. Extended, faint edge-brightened, soft X-ray lobes outside the optical galaxy are observed to a distance of 10 to 15 kpc on each side of the nuclear region. Bright plumes inside the optical isophotes coincide with the optical line emission and extend 11 kpc from end to end across the nucleus. The data for the plumes cannot be fit by a single temperature plasma, and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from bright, diffuse circumnuclear emission in the inner 3 kpc centered on the Halpha peak, which is displaced from the radio nuclei. There is a close morphological correspondence between the Halpha and soft X-ray emission on all spatial scales. We interpret the plumes as a starburst-driven superwind, and discuss two interpretations of the emission from the lobes in the context of simulations of the merger dynamics of Arp 220.

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arXiv2002

Axisymmetrical Gas Inflow in the Central Region of NGC 7331

New Integral Field Spectroscopy of the central region of NGC 7331 reveals strong H$α$ emission in the well-known CO and HI ring of NGC 7331. The [NII]/H$α$ ratio indicates that a large scale stellar formation process is taken place at the ring in agreement with previous hypothesis about the exhaustion of gas in the inner to the ring region. The dynamics of stars and gas are not coupled. There is a ring of peculiar velocities in the ionized gas velocity map. These peculiar velocities can be well interpreted by the presence of an axisymmetric inflow of 40 km/s at the inner boundary of the large-scale gaseous ring. We infer an inwards total flux of 1.6 M$_{\odot}$yr$^{-1}$. This value is typical of the accretion rates in hypothetical {\bf large} nuclear black holes. Despite the large differences in the scales of the nucleus and the gas ring of NGC 7331, we suggest that this inwards flux is feeding the nucleus.

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arXiv2002

Detection of the 2175ÅExtinction Feature at z=0.83

We determine the extinction curve in the z_l=0.83 lens galaxy of the gravitational lens SBS0909+532 from the wavelength dependence of the flux ratio between the lensed quasar images (z_s=1.38) from 3400 to 9200Å. It is the first measurement of an extinction curve at a cosmological distance of comparable quality to those obtained within the Galaxy. The extinction curve has a strong 2175Åfeature, a noteworthy fact because it has been weak or non-existent in most estimates of extinction curves outside the Galaxy. The extinction curve is fitted well by a standard $R_V=2.1\pm0.9$ Galactic extinction curve. If we assume standard Galactic extinction laws, the estimated dust redshift of $z=0.88\pm0.02$ is in good agreement with the spectroscopic redshift of the lens galaxy. The widespread assumption that SMC extinction curves are more appropriate models for cosmological dust may be incorrect.

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arXiv2000

The Diverse Population of ULIRGs

We present results from an on-going Hubble Space Telescope (HST) survey of a large sample of ULIRGs (Ultra-Luminous IR Galaxies). New ground-based observations are now being used to complement the HST data and to assist in the interpretation of these complex objects. A rich spectroscopic, morphological, and dynamical diversity is found within the ULIRG population, nearly 100% of which are merger and/or collision remnants. The consequences of this diversity may apply to the interpretation of distant submm/FIR sources and their subsequent evolution.

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arXiv2000

The Ultra-Luminous IR Galaxy Population

We summarize results from an on-going Hubble Space Telescope (HST) survey of a large sample of ULIRGs (Ultra-Luminous IR Galaxies). New ground-based multi-fiber spectroscopic observations are now being obtained to complement the HST data and to assist in the interpretation of these complex objects.

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arXiv2000

A detailed two-dimensional stellar population study of M32

We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region of M32 obtained with the 2D_FIS fibre spectrograph installed at the William Herschel Telescope. From these spectra line strength maps have been reconstructed for about 20 absorption lines, mostly belonging to the Lick system. We find good agreement with long-slit line strength profiles in the literature. In contrast with previous studies, indices were azimuthally averaged along continuum isophotes of M32. A remarkable result is that no gradients are presented in the spectral indices. So, we have fitted the mean values of each spectral index and central colours to the models of Vazdekis et al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and metallicity similar to solar (Z=0.02) are the best fitted values for the innermost region of M32.

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arXiv1999

Integral Field Spectroscopy of Mrk 273: Mapping 10^3 km/s Gas Flows and an Off-Nucleus Seyfert 2 Nebula

Integral field optical spectroscopy with the INTEGRAL fiber-based systemis used to map the extended ionized regions and gas flows in Mrk 273, one of the closest Ultraluminous Infrared galaxies (ULIRGs). The Hbeta and [OIII]5007 maps show the presence of two distinct regions separated by 4'' (3.1 kpc) along position angle (PA) 240. The northeastern region coincides with the optical nucleus of the galaxy and shows the spectral characteristics of LINERs. The southwestern region is dominated by [OIII] emission and is classified as a Seyfert 2. Therefore, in the optical, Mrk 273 is an ultraluminous infrared galaxy with a LINER nucleus and an extended off-nucleus Seyfert 2 nebula. The kinematics of the [OIII] ionized gas shows (i) the presence of highly disturbed gas in the regions around the LINER nucleus, (ii) a high-velocity gas flow with a peak-to-peak amplitude of 2.4 x 10^3 km/s, and (iii) quiescent gas in the outer regions (at 3 kpc). We hypothesize that the high-velocity flow is the starburst-driven superwind generated in an optically obscured nuclear starburst, and that the quiescent gas is directly ionized by a nuclear source, like the ionization cones typically seen in Seyfert galaxies.

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arXiv1998

Discovery of a Low-Mass Brown Dwarf Companion of the Young Nearby Star G196-3

A substellar-mass object in orbit at about 300 astronomical units (AU) from the young low-mass star G196-3 was detected by direct imaging. Optical and infrared photometry and low- and intermediate-resolution spectroscopy of the faint companion, hereafter referred to as G196-3B, confirms its cool atmosphere and allows its mass to be estimated at 25^{+15}_{-10} Jupiter masses. The separation between both objects and their mass ratio suggest the fragmentation of a collapsing cloud as the most likely origin for G196-3B, but alternatively it could have originated from a proto-planetary disc which has been dissipated. Whatever the formation process was, the young age of the primary star (about 100 Myr) demonstrates that substellar companions can form in short time scales.

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