Presentation on theme: "1 Dwarf Galaxies in the Universe Ovidiu Vaduvescu Conferinta Diasporei - Workshop Astronomie 22-24 Sep 2010 Bucharest, Romania."— Presentation transcript:
1 Dwarf Galaxies in the Universe Ovidiu Vaduvescu Conferinta Diasporei - Workshop Astronomie Sep 2010 Bucharest, Romania
2 Why dwarf galaxies and NIR? Because this was my proposed subject for my Canadian PhD starting in 2000 at York University in Toronto with Prof. Marshall McCall; Because dwarf galaxies are the most numerous galaxies in the Universe! Because they are quite simple to study, believed to be the first galaxies to form, from which larger ones evolve); Because they are little studied, being very difficult to observe (requiring large telescopes and extended time), due to their extremely faint brightness! Why observing in Near Infrared (NIR) and not in visible? - Because NIR is more transparent to dust (internal or Galactic) - Because NIR light traces better the stellar mass of a galaxy.
3 Observing runs OAN-SPM 2.1m, Mexico (10n, 2001 & 2003) CFHT 3.6m, Hawaii (6n, 2002 & 2004) Gemini North 8.1m, Hawaii (12h service, 2003) Gemini South 8.1m, Chile (40h, 2007, 2008 & 2010) NTT ESO 3.5m, La Silla, Chile (5n, 2006 & 2008) VLT ESO 8.2m, Paranal, Chile (6h, 2008) TNG 3.5m, La Palma (4n, 2010) INT 2.5m, La Palma (10n, 2009 & 2010)
4 Observing in the NIR More difficult than in visible! It is important how you observe in the NIR (how often you sample the sky to be subtracted every minute). We invented a smart algorithm to subtract the sky in the NIR. (Vaduvescu & McCall, 2004)
5 KILLALL, an IRAF software to remove stars from an image There are about 5000 stars in the first image, including about 2500 on top of the galaxy! They can be removed semi- automatically in 5 steps using KILLALL. Buta & McCall, 1999 (UNIX) Vaduvescu & McCall, 2001 (ported in Linux)
6 Dwarf Irregular Galaxies (dIs) They have surface brightness profiles (SBPs) linear in the outer part and bounding horizontal at the centre. SBPs can be fitted with the new “sech” law (Vaduvescu & McCall, 2005): Why is this? Not known! Needs to be investigated (modeling). Collaborators welcomed!
7 The dIs Fundamental Plane (FP) Three physical parameters linking dIs in a FP in the NIR (Vaduvescu & McCall 2008): - Sech absolute mag M S - Central surface bright o - Hydrogen line width W20 (from radio data) Why is this? Not known! Work in progress; an improved FP soon (Vaduvescu et al 2010) The FP can be used as a new distance indicator: if we measure these quantities, then we can calculate M, then the galaxy distance modulus DM = m - M = 5 log (d) - 5 then, the galaxy distance!
8 NIR CMDs of dIs Near Infrared (NIR) Color-Magnitude Diagrams (CMDs) for the stars resolved in two dwarf irregular (dIs) galaxies. Two main details can be seen: the main bulk and a “finger” (Vaduvescu et al 2005). Could the “whole” be real? Needs more study, collaborators welcomed.
9 Blue Compact Dwarf Galaxies (BCDs) BCDs have surface brightness profiles linear at the outer parts and growing then bounding horizontal at the centre. Fitted with the “sech” law to count the outer regions (dashed line) plus a Gaussian to model the central BCD starburst (dotted line), Vaduvescu & McCall, 2006:
10 BCDs and the dIs FP Blue Compact Dwarfs (BCDs) appear to be located on the Fundamental Plane (FP) defined by the dwarf irregulars (dIs). This probes a physical link between the two dwarf classes. The FP stands as a distance indicator for BCDs also (Vaduvescu, Richer & McCall, 2006)
11 Dwarf Ellipticals (dEs) and the dIs FP Dwarf Elliptical galaxies (dEs) stand on the dIs FP, suggesting a physical link between the three dwarf classes (dIs, BCDs and dEs). In comparison (left), Tully Fisher relation shows larger scatter (Vaduvescu & McCall, 2005). New dE data available recently (collaborators from NL)to probe this New dE data available recently (collaborators from NL) to probe this (collaborators welcomed)!
12 Chemical evolution of dIs and BCDs Chemical properties in star forming dwarf galaxies can be measured via spectroscopy, counting the oxygen abundance. Best results are achieved via [OIII] 4363 line (“direct method”), but this is very faint to observe, requiring ~8m class telescopes. Alternatively, other bright line methods exist (less accurate) (Vaduvescu, McCall & Richer 2007).
13 Chemical evolution of dIs and BCDs Oxygen abundance correlates with absolute sech magnitude in both dIs and BCDs, and in the NIR the relation is tightest (Vaduvescu, Richer & McCall 2007)
14 Chemical evolution of dIs and BCDs Oxygen abundance correlates with baryonic (visible) mass of dIs and BCDs in a similar relation (Vaduvescu, Richer & McCall 2007)
15 Dwarf evolution in clusters Compare star forming galaxy isolated evolution (Local Volume d<10 Mpc) with dwarf galaxy evolution in nearby galaxy clusters (d<100 Mpc): Virgo (14 Mpc) Fornax (17 Mpc) Hydra (49 Mpc) Antlia (35 Mpc) Perseus (5 Mpc) Abell 779 (92 Mpc) Abell 1367 (90 Mpc) Vaduvescu et al, 2010 (incl. Gemini & VLT data, paper to submit soon) show similar evolutions of star forming dwarfs in Virgo, Fornax and Hydra. New data (H and NIR imaging) was acquired recently for the other clusters, being reduced now (collaborations from Spain).
16 Collaborators Prof. Marshall McCall, York Univ, Canada; Drd. Robin Fingerhut, York Univ, Canada; Dr. Astron. Michael Richer, OAN-SPM, Mexico; Prof. Dr. Jose Vilchez, IAA, Granada, Spain; Dr. Carolina Kehrig, Potsdam Institute Astronomy, Germany; Dr. Jorje Iglesias-Paramo, IAA, Granada, Spain; Drd. Vasiliky Petropoulou, IAA, Granada, Spain; Prof. Dr. Eduardo Unda-Sanzana, IAA, UCN, Chile; Dr. Marcus Albrecht, Univ. Bonn, Germany; Others welcomed to probe dEs and possibly new giant galaxy connections!
17 References Vaduvescu, O. and McCall, M., 2004, PASP 116, 640 "Strategies for Imaging Faint Extended Sources in the Near-Infrared" Vaduvescu, O. et al, 2005, AJ 130, 1593 "Infrared Properties of Star-Forming Dwarf Galaxies. I. Dwarf Irregular Galaxies in the Local Volume" Vaduvescu, O., Richer, M., and McCakll, M., 2006, AJ 131, 1318 "Infrared Properties of Star-Forming Dwarf Galaxies. II. Blue Compact Dwarf Galaxies in the Virgo Cluster" Vaduvescu, O. and McCall, M., 2005, Proc. IAU No. 198 "dEs and the dI fundamental plane" Vaduvescu, O., McCall, M. and Richer, M., 2007, AJ 134, 604 "Chemical Properties of Star-Forming Dwarf Galaxies" Vaduvescu, O. and McCall, M., 2008, A&A 487, 147 "The fundamental plane of dwarf irregular galaxies" Vaduvescu, O., et al. 2010, to be submitted soon to A&A "Searching for Star Forming Galaxies in Fornax and Hydra Clusters" Vaduvescu, O., et al. 2010, to be submitted soon to A&A "Mapping the Local Universe with the Dwarf Fundamental Plane"