M. Rosado

A Multiwavelength Study of Stephan's Quintet

Stephans Quintet (SQ) is a compact group that we find in an atypical moment when a high-velocity intruder is passing through it. The intrusion is particularly interesting because a previous intruder had stripped most of the gas from the group members. This debris field was shocked in the ongoing collision with the new intruder. This evolutionary history agrees well with observations and explains how a strongly interacting system can show low levels of star formation. We present new multiwavelength data including previously unpublished ROSAT X-ray, Hα interference filter/Fabry-Perot, ISO MIR/FIR, and radio line and continuum images. These observations and previously published data provide new insights, as well as support for some previous hypotheses. (1) Fabry-Perot and H I velocities allow us to unambiguously distinguish between gas associated with SQ and the new intruder. (2) Most detected emission regions are found in the remnant interstellar medium (ISM) of the new intruder, which allows us to infer its size and present physical state. (3) The few emission regions associated with the stripped ISM of SQ include the best candidate tidal dwarf galaxy. (4) Multiwavelength data suggest that strong MIR/FIR emission from the Seyfert 2 nucleus of NGC 7319 comes from dust heated directly by a power-law continuum rather than a starburst. (5) The correspondence between extended X-ray/radio continuum/forbidden optical emission confirms the existence of a large scale shock in SQ. (6) We confirm the presence of two stripped spiral members in the process of transformation into E/S0 morphology. Finally (7) observations are consistent with the idea that the collision in SQ is ongoing with possible detection of H II region ablation and Rayleigh-Taylor instabilities.

IC 10: More evidence that it is a blue compact dwarf

We present optical spectroscopy of Hii regions in the Local Group galaxy IC 10 and UBVR photometry of foreground stars in three fields towards this galaxy. From these data, we find that the foreground reddening due to the Milky Way is

Destruction of the Environment of the BN-KL Nebula

E(B-V)=0.77\pm 0.07 \mathrm{mag}

Interstellar Bubbles in Two Young H II Regions

. We find that IC 10 contains considerable internal dust, which qualitatively explains the variety of reddening values found by studies of its different stellar populations. Based upon our foreground reddening, IC 10 has intrinsic photometric properties like those of a blue compact dwarf galaxy, and not those of a dwarf irregular. This result is consistent with much evidence that IC 10 is in the throes of a starburst that began at least

Interstellar Bubbles in Two Young HII Regions

10 \mathrm{Myr}

Diffuse X-Ray Emission from the Quiescent Superbubble M17, the Omega Nebula

ago. We also report the discovery of a new WR star in the Hii region HL111c.

Kinematics of the ionized gas in the Local Group irregular galaxy IC 1613

Resumen en: We present the velocity structure of the 2.12 micron H2 emission in Orion, obtained with an IR Fabry-Perot interferometer with a spectral resolution of 2...

The isolated interacting galaxy pair NGC 5426/27 (Arp 271)

Massive stars are expected to produce wind-blown bubbles in the interstellar medium; however, ring nebulae, suggesting the existence of bubbles, are rarely seen around main-sequence O stars. To search for wind-blown bubbles around main-sequence O stars, we have obtained high-resolution Hubble Space Telescope WFPC2 images and high-dispersion echelle spectra of two pristine HII regions, N11B and N180B, in the Large Magellanic Cloud. These HII regions are ionized by OB associations that still contain O3 stars, suggesting that the HII regions are young and have not hosted any supernova explosions. Our observations show that wind-blown bubbles in these HII regions can be detected kinematically but not morphologically because their expansion velocities are comparable to or only slightly higher than the isothermal sound velocity in the HII regions. Bubbles are detected around concentrations of massive stars, individual O stars, and even an evolved red supergiant (a fossil bubble). Comparisons between the observed bubble dynamics and model predictions show a large discrepancy (1--2 orders of magnitude) between the stellar wind luminosity derived from bubble observations and models and that derived from observations of stellar winds. The number and distribution of bubbles in N11B differ from those in N180B, which can be explained by the difference in the richness of stellar content between these two HII regions. Most of the bubbles observed in N11B and N180B show a blister-structure, indicating that the stars were formed on the surfaces of dense clouds. Numerous small dust clouds, similar to Bok globules or elephant trunks, are detected in these HII regions and at least one of them hosts on-going star formation.

SEYFERT'S SEXTET: A SLOWLY DISSOLVING STEPHAN'S QUINTET?

Massive stars are expected to produce wind-blown bubbles in the interstellar medium; however, ring nebulae, suggesting the existence of bubbles, are rarely seen around main-sequence O stars. To search for wind-blown bubbles around main-sequence O stars, we have obtained high-resolution Hubble Space Telescope WFPC2 images and high-dispersion echelle spectra of two pristine HII regions, N11B and N180B, in the Large Magellanic Cloud. These HII regions are ionized by OB associations that still contain O3 stars, suggesting that the HII regions are young and have not hosted any supernova explosions. Our observations show that wind-blown bubbles in these HII regions can be detected kinematically but not morphologically because their expansion velocities are comparable to or only slightly higher than the isothermal sound velocity in the HII regions. Bubbles are detected around concentrations of massive stars, individual O stars, and even an evolved red supergiant (a fossil bubble). Comparisons between the observed bubble dynamics and model predictions show a large discrepancy (1--2 orders of magnitude) between the stellar wind luminosity derived from bubble observations and models and that derived from observations of stellar winds. The number and distribution of bubbles in N11B differ from those in N180B, which can be explained by the difference in the richness of stellar content between these two HII regions. Most of the bubbles observed in N11B and N180B show a blister-structure, indicating that the stars were formed on the surfaces of dense clouds. Numerous small dust clouds, similar to Bok globules or elephant trunks, are detected in these HII regions and at least one of them hosts on-going star formation.

Kinematics of the Molecular Hydrogen from the Planetary Nebula NGC 2346

The emission nebula M17 contains a young ~1 Myr old open cluster; the winds from the OB stars of this cluster have blown a superbubble around the cluster. ROSAT observations of M17 detected diffuse X-ray emission peaking at the cluster and filling the superbubble interior. The young age of the cluster suggests that no supernovae have yet occurred in M17; therefore, it provides a rare opportunity to study hot gas energized solely by shocked stellar winds in a quiescent superbubble. We have analyzed the diffuse X-ray emission from M17 and compared the observed X-ray luminosity of ~2.5 × 1033 ergs s-1 and the hot gas temperature of ~8.5 × 106 K and mass of ~1 M☉ to model predictions. We find that bubble models with heat conduction overpredict the X-ray luminosity by 2 orders of magnitude; the strong magnetic fields in M17, as measured from H I Zeeman observations, have most likely inhibited heat conduction and associated mass evaporation. Bubble models without heat conduction can explain the X-ray properties of M17, but only if cold nebular gas can be dynamically mixed into the hot bubble interior and the stellar winds are clumpy with mass-loss rates reduced by a factor of ≥3. Future models of the M17 superbubble must take into account the large-scale density gradient, small-scale clumpiness, and strong magnetic field in the ambient interstellar medium.