arXiv subjects

Claude Carignan

Publications and source records attributed to Claude Carignan.

63 records · Page 4Linked to original sources

arXiv2002

Multiwavelength Rotation Curves to Test Dark Halo Central Shapes

We use Fabry-Perot Halpha spectroscopy, complemented with published HI radio synthesis observations to derive high resolution rotation curves of spiral galaxies. We investigate precisely their inner mass distribution and compare it to CDM simulations predictions. Having verified the existence of the so-called core-cusp problem, we find that the dark halo density inner slope is related to the galaxy masses. Dwarf galaxies with V_max < 100 km/s have halo density inner slope 0 < γ< 0.7 while galaxies with V_max > 100 km/s are best fitted by γ>= 1.

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arXiv2001

Accurate Determination of the Mass Distribution in Spiral Galaxies: II. Testing the Shape of Dark Halos

New high resolution CFHT Fabry-Perot data, combined with published VLA 21 cm observations are used to determine the mass distribution of NGC 3109 and IC 2574. The multi-wavelength rotation curves allow to test with confidence different dark halo functional forms from the pseudo-isothermal sphere to some popular halo distributions motivated by N-body simulations. It appears that density distribution with an inner logarithmic slope <= -1 are very hard to reconcile with rotation curves of late type spirals. Modified Newtonian Dynamics (MOND) is also considered as a potential solution to missing mass and tested the same way. The new higher resolution data show that MOND can reproduce in details the rotation curve of IC 2574 but confirm its difficulty to fit the kinematics of NGC 3109.

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arXiv2000

The Impact of External Tidal Fields on the ISM of Dwarf Spheroidals

It was found that for three dwarf spheroidal galaxies - Sculptor, Tucana, and Cetus - there is a correspondence between the distribution of associated HI gas and the projected tidal axis direction. Numerical hydrodynamical simulations confirmed the following scenario: SN Ia explosions remove most of the interstellar medium beyond the tidal radius of the dwarf galaxy, with most of the mass being in clouds moving along the principal tidal axis.

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arXiv1999

Accurate Parameters of the Mass Distribution in Spiral Galaxies: 1. Fabry - Perot Observations of NGC 5585

Using the example of the Sd galaxy NGC 5585, it is shown that high resolution 2-D HII kinematical data are necessary to determine accurately the parameters of the mass distribution in spirals. New CFHT Fabry-Perot Halpha observations are combined with low resolution (20") Westerbork HI data to study its mass distribution. Using the combined rotation curve and best fit models, it can be seen that M/L of the luminous disk goes from 0.3 using only the HI rotation curve, to 0.8 using both the optical and the radio data. This reduces the dark-to-luminous mass ratio in NGC 5585 by ~30% through increasing the dark matter halo core radius by nearly the same amount. This shows the importance of the inner, rising part of the rotation curve for the accurate determination of the parameters of the global mass (luminous & dark) distribution and suggests that such a fine tuning of the rotation velocities using high resolution 2-D HII kinematics is necessary to look at correlations between the parameters of the dark matter component and other properties of galaxies.

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arXiv1998

Necessity for High Accuracy Rotation Curves in Spiral Galaxies

In the last 20 years, rotation curves derived from H I kinematics obtained on radio synthesis instruments were used to probe the dark matter distribution in spiral and dwarf irregular galaxies. It is shown, with the aid of the Sd galaxy NGC 5585, that high resolution 2--D H II kinematics is necessary to determine accurately the mass distribution of spirals. New CFHT Fabry--Perot Hff observations are combined with low resolution Westerbork H I data to study its mass distribution. Using the combined rotation curve and best fit models, it can be seen that the (M/LB) of the luminous disk goes from 0.3, using only the H I rotation curve, to 0.8, using both the optical and the radio data. This reduces the dark--to--luminous mass ratio by 30%.

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arXiv1998

Detection of HI associated with the Sculptor Dwarf Spheroidal Galaxy

Neutral hydrogen (HI) has been detected in the Local Group dwarf spheroidal galaxy Sculptor with the 64 m Parkes single dish and mapped with the Australia Telescope synthesis array. Most of the detected HI is in two clouds \sim 15'-20' away from the optical center. The gas is observed at the same systemic velocity than the stars but at \ge 125 \kms away from the Magellanic Stream components in that region. A lower limit to the HI mass of 3.0 \times 10^4 \Msol is derived from the synthesis observation for an M_HI/L_B \simeq 0.02. This amount of HI is compatible with mass loss expected from normal giants even if only 10% of the gas is retained by the galaxy in its neutral form.

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arXiv1997

Mass-Models of Five Nearby Dwarf Irregular Galaxies

Five nearby dwarf irregular galaxies, amongst the recently surveyed dwarf members of the Sculptor and Centaurus A groups (at 2.5 Mpc and 3.5 Mpc), have been imaged in neutral hydrogen (HI) with the Australia Telescope and the Very Large Array. These objects have absolute magnitudes M_B in the range -14.9 to -12.7, yet they are clearly rotationally supported, with maximum rotation velocities ranging from 43 km/s to 67 km/s. Multi-component mass-models have been fitted to the rotation curves. We investigate the properties of their dark matter halos, and the scaling laws of the dark matter halos parameters.

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arXiv1997

NGC 5084: A Massive Disk Galaxy Accreting its Satellites ?

The spectra of 34 galaxies within 20 arcmins (\sim 100 kpc) of the lenticular galaxy NGC 5084 have been obtained using the FOCAP system on the Anglo-Australian 3.9m telescope. Nine objects are found with projected separations \lesssim 80 kpc and with radial velocities within \pm 630 km/s of the parent galaxy redshift. Using various techniques, their velocity differences and projected separations are used to estimate the mass of this S0 galaxy, which ranges from 6 \times 10^{12} M_{\odot} to 1 \times 10^{13} M_{\odot}. With such a mass, NGC 5084 is one of the most massive disk galaxy known, with a M/L_B \gtrsim 200 M_{\odot}/L_{\odot}. In agreement with the models' predictions of Quinn & Goodman (1986) but contrary to the results of Zaritsky et al (1993) obtained from their statistical sample, the properties of the satellites' population show no evidence for the "Holmberg effect", and a clear excess of satellites in retrograde orbits. Several signs hint that this S0 galaxy has survived the accretion of several satellites.

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arXiv1997

Discovery of Numerous Dwarf Galaxies in the Two Nearest Groups of Galaxies

We report the discovery of a large population of dwarf irregular galaxies in the two nearest groups of galaxies outside the Local Group, the Sculptor and the Centaurus A groups (2.5 and 3.5 Mpc). Total areas of approximately 940 and 910 square degrees in these groups were scanned visually on the SRC J films to find dwarf candidates. Redshifts were obtained by an HI survey carried out at Parkes, with detection limits of 4 \times 10^6 \Msun and 7.8 \times 10^6 \Msun , and 33 dwarf galaxies were successfully detected in the groups. A follow-up optical survey (Halpha spectroscopy) detected a few more, and confirmed most of the HI redshifts. A total of 16 and 20 dwarf galaxies are found in Sculptor and Centaurus A, of which 6 are newly identified objects, and 5 more have newly determined redshifts. In both groups the dwarf members show a wider spatial and velocity distribution than the brighter members. From their radial velocities and projected distances we estimate the crossing times of the groups, which confirm that they are not yet virialised.

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