arXiv subjects

Petri Vaisanen

Publications and source records attributed to Petri Vaisanen.

22 records · Page 2Linked to original sources

arXiv2009

Star formation properties and dynamics of Luminous Infrared Galaxies with adaptive optics

Near infrared adaptive optics observations are crucial to be able to interpret kinematic and dynamical data and study star formation properties within the often extremely dusty interacting luminous IR galaxies (LIRGs). NIR AO data are also needed to find supernovae in their bright and dusty central regions and to fully characterize the young stellar clusters found in these kinds of systems. We have used AO in the K-band to survey a sample of LIRGs at 0.1 arcsec (30 to 100 pc) resolution. The data are merged with SALT and AAT spectroscopic follow-up and HST and Spitzer archival imaging. The first AO detected SNe are reported as well as details of the first studied LIRGs. One LIRG showed an unexpected third component in the interaction, which moreover turned out to host the most active star formation. Another target showed evidence in the NIR of a very rare case of leading spiral arms, rotating in the same direction as the arms open.

astro-ph.CO↗

arXiv2008

A pair of leading spiral arms in a luminous infrared galaxy?

Leading spiral arms are a rare phenomenon. We present here one of the very few convincing candidates of spiral arms opening counter-intuitively in the same direction as the galaxy disk is rotating. This detection in a luminous IR galaxy (LIRG) IRAS 18293-3134 is based on near infrared (NIR) adaptive optics imaging with the Very Large Telescope and long-slit NIR spectroscopy with the Anglo-Australian Telescope. We discuss the orientation of the galaxy based on imaging and derive rotation curves from both emission and absorption features in the spectrum. The galaxy is strongly star-forming and has a minor companion in a high-velocity encounter. The fact that the arms of IRAS 18293-3134 are not easily traceable from optical images suggests that larger samples of high-quality NIR imaging of interacting systems and LIRGs might uncover further cases of leading arms, placing constraints on spiral arm theories and retrograde encounters, and especially on the relationship between disk masses and dark matter halo masses.

astro-ph↗

arXiv2008

Determining the extragalactic extinction law with SALT

We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11mu m^{-1} < lambda^{-1} < 2.94 mu m^{-1} by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic enviroment are similar to those of the Milky Way. The ratio of the total V band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82+-0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust.

astro-ph↗

arXiv1996

Extragalactic background light: the contribution by faint and low surface brightness galaxies

Several models which have been constructed to explain the faint galaxy excess in observed number counts are used to predict the intensity of the extragalactic background light (EBL). Special attention is given to irregular and dwarf galaxies, which seem to be more common in the universe than once thought, and to low surface brightness galaxies (LSB), which can in principle be altogether missed from galaxy counts. The nature of the latter objects is still unclear, but some plausible models predict that LSB galaxies can increase the intensity of the EBL by a factor of up to 5 from a standard, no-evolution model in the optical and near infrared and by an order of magnitude in the UV. If the faint excess population consists of low-luminosity dwarfs, whose luminosity function has a steep faint end, the EBL can well increase by a factor of 3 to 5, while still being consistent with current number count data. The resulting values of the EBL are not far from the observed upper limits. In the future the overall level of the EBL and its spectral distribution could be used to differentiate between galaxy population models.

astro-ph↗