Dwarf GalaxiesDwarf Galaxies

Ovidiu VaduvescuOvidiu Vaduvescu

ING and IAC AssociatedING and IAC Associated

ING+NOT+Mercator SeminarING+NOT+Mercator Seminar31 May 2012, La Palma31 May 2012, La Palma

AbstractAbstract

Brief overview about science interests of studying star forming Brief overview about science interests of studying star forming dwarf galaxies: dwarf irregulars (dIs) and blue compact dwarfs dwarf galaxies: dwarf irregulars (dIs) and blue compact dwarfs (BCDs); (BCDs);

Strategies for NIR imaging of extremely faint targets. Our smart Strategies for NIR imaging of extremely faint targets. Our smart algorithm to subtract the highly variable NIR sky; algorithm to subtract the highly variable NIR sky;

Our new sech law to fit SBPs of dIs and BCDs; Our new sech law to fit SBPs of dIs and BCDs; Our new “dwarf fundamental plane” (FP) fitting dIs, BCDs and dEs. Our new “dwarf fundamental plane” (FP) fitting dIs, BCDs and dEs.

Some physical fundamentals of this FP; Some physical fundamentals of this FP;

Chemical evolution of dIs and BCDs in clusters and isolated; Chemical evolution of dIs and BCDs in clusters and isolated;

Future projects and search for students/collaborators at Future projects and search for students/collaborators at ING/NOT/IAC/etc. ING/NOT/IAC/etc.

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Why dwarf galaxies and NIR?Why dwarf galaxies and NIR?

Because this was my proposed subject for my Canadian PhD (2000-Because this was my proposed subject for my Canadian PhD (2000-2005) at York University in Toronto (Prof. Marshall McCall); 2005) at York University in Toronto (Prof. Marshall McCall);

Because dwarf galaxies are the most numerous galaxies in the Because dwarf galaxies are the most numerous galaxies in the Universe! Universe!

Because they should be the most simple to study, believed to be Because they should be the most simple to study, believed to be the first galaxies to form, from which the larger ones evolved; the first galaxies to form, from which the larger ones evolved;

Because they are little studied, being very difficult to observe Because they are little studied, being very difficult to observe (requiring large telescopes and long time), due to their extremely (requiring large telescopes and long time), due to their extremely faint brightness! faint brightness!

Why observing in Near Infrared (NIR) and not in visible?Why observing in Near Infrared (NIR) and not in visible?

- Because NIR light traces better the stellar mass of a galaxy; - Because NIR light traces better the stellar mass of a galaxy;

- Because NIR is more transparent to dust (internal or Galactic). - Because NIR is more transparent to dust (internal or Galactic).

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Observing runs: 2-8m Observing runs: 2-8m telescopestelescopes

OAN-SPM Camila (10n, 2001 & 2003)OAN-SPM Camila (10n, 2001 & 2003)

CFHT CFHTIR (6n, 2002 & 2004)CFHT CFHTIR (6n, 2002 & 2004)

Gemini North GMOS-N (12h spec, 2003)Gemini North GMOS-N (12h spec, 2003)

Gemini South GMOS-S (50h Ha img & spec, 2007-2012)Gemini South GMOS-S (50h Ha img & spec, 2007-2012)

NTT SOFI (5n, 2006 & 2008)NTT SOFI (5n, 2006 & 2008)

Blanco ISPI (10n, 2006-2009)Blanco ISPI (10n, 2006-2009) VLT HAWK-I (6h, 2008)VLT HAWK-I (6h, 2008)

TNG NICS (4n, 2010)TNG NICS (4n, 2010)

INT WFC (10n Ha img, 2009 & 2010)INT WFC (10n Ha img, 2009 & 2010)

SAAO IRSF SIRIUS (collab, 2005 & 2006)SAAO IRSF SIRIUS (collab, 2005 & 2006)

CFHT WIRCAM (collab, 2005 & 2006)CFHT WIRCAM (collab, 2005 & 2006)

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Observing in the NIR:Observing in the NIR:The problem with the rapidly variable sky (in level and structure)The problem with the rapidly variable sky (in level and structure)

More difficult than in visible! More difficult than in visible!

It is very important HOW we It is very important HOW we observe in the NIR (how often observe in the NIR (how often sample the sky to be sample the sky to be subtracted every ~minute). subtracted every ~minute).

Movie showing Mauna Kea Movie showing Mauna Kea sky and CFHT environment sky and CFHT environment variations in Ks band during 2 variations in Ks band during 2 min step (timelapse 20 min). min step (timelapse 20 min). Variations across the 3.6' Variations across the 3.6' CFHT-IR chip about 1% of the CFHT-IR chip about 1% of the sky level are visible. sky level are visible.

(Vaduvescu & McCall, 2004)(Vaduvescu & McCall, 2004)

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Observing faint galaxies in the NIRObserving faint galaxies in the NIR

Giving the sequence:Giving the sequence:sky-gal-sky-gal-sky-gal-sky-gal-sky-....sky-....

If one combines the If one combines the sky observed less sky observed less frequently, the final frequently, the final combined galaxy combined galaxy gets worse. gets worse.

Thus, a so-called Thus, a so-called “superflat” in the NIR “superflat” in the NIR destroys the destroys the temporal sky temporal sky variation! variation!

We invented a smart We invented a smart algorithm to “build” algorithm to “build” and subtract the sky and subtract the sky “under” the galaxies “under” the galaxies in the NIR. in the NIR.

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Our algorithm to reduce NIR imagesOur algorithm to reduce NIR images

Step 1Step 1: raw sky: raw sky

How to build and subtract the sky “under” the galaxyHow to build and subtract the sky “under” the galaxyassuming the observing sequence sky1-gal1-sky2-assuming the observing sequence sky1-gal1-sky2-

gal2-....gal2-....

Step 2:Step 2: Subtract sky1-sky2 Subtract sky1-sky2 (to see all stars)(to see all stars)

Step 3:Step 3: find all stars find all stars (daofind)(daofind)Steps 4-6: mask stars (imedit or daophot/PSF)

Step 7:Step 7: add back raw sky2 add back raw sky2 (to fill back all black holes)(to fill back all black holes)

Step 8:Step 8: do these again for do these again for sky2-sky1 and average the sky2-sky1 and average the final reduced sky to final reduced sky to interpolate timeinterpolate timeRemember first raw Remember first raw sky/sky/step1step1??

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Our algorithm to reduce NIR imagesOur algorithm to reduce NIR imagesHow an extremely faint galaxy shows up following accurate sky How an extremely faint galaxy shows up following accurate sky

subtractionsubtraction

Step 2 gal:Step 2 gal: galaxy sky galaxy sky subtracted (sky built like subtracted (sky built like before)before)Step 3 gal:Step 3 gal: combined combined galaxy (some black hole galaxy (some black hole residuals due to bright residuals due to bright stars, background galaxies stars, background galaxies in the sky field or in the sky field or insufficient large dithering)insufficient large dithering)Step 4 gal: mask residuals(manual imedit or other) – final reduced galaxy image

Remember first raw galaxy Remember first raw galaxy ((step1)step1)??

Step 1 gal:Step 1 gal: raw galaxy raw galaxy (can you find it? :)(can you find it? :)

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KILLALL, an IRAF software KILLALL, an IRAF software to remove stars from an imageto remove stars from an image

NGC 1569 (our most NGC 1569 (our most complicated studied complicated studied dwarf):dwarf):

There are about 5000 There are about 5000 stars in the first image, stars in the first image, including some 2500 on including some 2500 on top of the galaxy! top of the galaxy!

They can be removed They can be removed semi-automatically in 5 semi-automatically in 5 steps using KILLALL steps using KILLALL (DAOPHOT/PSF based (DAOPHOT/PSF based script) one day workscript) one day work

Buta & McCall, 1999 Buta & McCall, 1999 (UNIX)(UNIX)

Vaduvescu & McCall, Vaduvescu & McCall, 2001 (ported in Linux)2001 (ported in Linux)

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Dwarf Irregular Galaxies (dIs)Dwarf Irregular Galaxies (dIs)

They have surface They have surface brightness profiles (SBPs) brightness profiles (SBPs) linear in the outer part linear in the outer part and bounding horizontal and bounding horizontal at the centre. at the centre.

We invented a new We invented a new “sech” law to fit SBPs of “sech” law to fit SBPs of dIs (Vaduvescu et al, dIs (Vaduvescu et al, 2005): 2005):

Why is this? Not known. Why is this? Not known. Could be investigated Could be investigated (modeling – (modeling – collaborators?)collaborators?)

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The dIs Fundamental Plane (FP)The dIs Fundamental Plane (FP)The linear Tully-Fisher The linear Tully-Fisher relation does not appear to relation does not appear to hold for dIs.hold for dIs.Instead, three physical Instead, three physical parameters link dIs in a parameters link dIs in a Fundamental Plane (FP) Fundamental Plane (FP) (Vaduvescu et al., 2005, (Vaduvescu et al., 2005, Vaduvescu & McCall, 2008): Vaduvescu & McCall, 2008):

- Sech absolute mag M- Sech absolute mag MSS - Central surface brightness o - Hydrogen line width W20 (radio)

This FP can be used as a new This FP can be used as a new distance indicator (for dwarfs distance indicator (for dwarfs or others): if we measure or others): if we measure oo and Wand W

2020, then we can , then we can

calculate M, thus the galaxy calculate M, thus the galaxy distance modulus and distance modulus and distance! distance!

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Fundamentals of the dwarf FPFundamentals of the dwarf FP

The baryonic potential plane assuming fixed M/L (left) The baryonic potential plane assuming fixed M/L (left) and individualized virial conditions (right). and individualized virial conditions (right).

Standard deviations are 0.29 mag, similar to that of TF relation for Standard deviations are 0.29 mag, similar to that of TF relation for giants! giants!

(McCall, Vaduvescu et al., 2012)(McCall, Vaduvescu et al., 2012)12

NIR CMDs of dIsNIR CMDs of dIs

Near Infrared (NIR) Color-Magnitude Diagrams (CMDs) for the stars Near Infrared (NIR) Color-Magnitude Diagrams (CMDs) for the stars resolved in two dwarf irregular (dIs) galaxies. Two main details can be resolved in two dwarf irregular (dIs) galaxies. Two main details can be seen: the main bulk and a “finger” (Vaduvescu et al 2005). Is the tilt seen: the main bulk and a “finger” (Vaduvescu et al 2005). Is the tilt

metallicity-dependent?metallicity-dependent?Is the “whole” real? Again, collaborators welcomed! Is the “whole” real? Again, collaborators welcomed! 13

Blue Compact Dwarf Galaxies (BCDs)Blue Compact Dwarf Galaxies (BCDs)

BCDs have surface BCDs have surface brightness profiles linear at brightness profiles linear at the outer parts and growing the outer parts and growing then bounding horizontal at then bounding horizontal at the centre. the centre.

Fitted with the “sech” law Fitted with the “sech” law to count the outer regions to count the outer regions (dashed line) plus a (dashed line) plus a Gaussian to model the Gaussian to model the central BCD starburst central BCD starburst (dotted line) - Vaduvescu, (dotted line) - Vaduvescu, Richer & McCall, 2006: Richer & McCall, 2006:

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BCDs and the dIs FPBCDs and the dIs FP

Blue Compact Dwarfs Blue Compact Dwarfs (BCDs) (BCDs) seem to be located on the seem to be located on the FP defined by dIs. FP defined by dIs.

This probes a physical link This probes a physical link between the two dwarf between the two dwarf classes. classes.

The FP stands as a distance The FP stands as a distance indicator for BCDs, also. indicator for BCDs, also.

(Vaduvescu, Richer & (Vaduvescu, Richer & McCall, 2006)McCall, 2006)

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Dwarf Ellipticals (dEs) and the dIs FPDwarf Ellipticals (dEs) and the dIs FP

Dwarf Elliptical galaxies (dEs) stand on the dIs FP, suggesting a physical Dwarf Elliptical galaxies (dEs) stand on the dIs FP, suggesting a physical link between the three dwarf classes (dIs, BCDs and dEs) (Vaduvescu & link between the three dwarf classes (dIs, BCDs and dEs) (Vaduvescu &

McCall 2005). McCall 2005). In comparison (left), Tully Fisher relation shows larger scatter (Vaduvescu In comparison (left), Tully Fisher relation shows larger scatter (Vaduvescu

et al, 2005). New dE NIR data available to probe this (collaborators et al, 2005). New dE NIR data available to probe this (collaborators welcomed)! welcomed)!

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Chemical evolution of dIs and BCDsChemical evolution of dIs and BCDsChemical properties in Chemical properties in star forming dwarf star forming dwarf galaxies can be galaxies can be measured via measured via spectroscopy, namely spectroscopy, namely the oxygen the oxygen abundance. abundance.

Best results are Best results are achieved via [OIII] achieved via [OIII] 4363 line (“direct 4363 line (“direct method”), but this is method”), but this is very faint to observe, very faint to observe, requiring ~8-10m class requiring ~8-10m class telescopes (=> GTC !)telescopes (=> GTC !)

Alternatively, use other Alternatively, use other bright line methods bright line methods (less accurate) (less accurate)

(Vaduvescu, McCall & (Vaduvescu, McCall & Richer, 2007)Richer, 2007)

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Chemical evolution of dIs and BCDsChemical evolution of dIs and BCDs

Oxygen abundance Oxygen abundance correlates with absolute correlates with absolute sech magnitude in both dIs sech magnitude in both dIs and BCDs, and in the NIR and BCDs, and in the NIR the relation is tighter than the relation is tighter than in visiblein visible

12+log(O/H)=5.58-12+log(O/H)=5.58-0.14log(M0.14log(M

SS))

(rms=0.10)!(rms=0.10)!

(Vaduvescu, Richer & (Vaduvescu, Richer & McCall 2007)McCall 2007)

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Chemical evolution of dIs and BCDsChemical evolution of dIs and BCDs

In a closed box model, In a closed box model, metallicity is expected to metallicity is expected to correlate with the gas correlate with the gas fraction, fraction,

μ = Mgas/(Mgas+Mstars)μ = Mgas/(Mgas+Mstars)

BCDs and dIs appear to BCDs and dIs appear to obey this model (although obey this model (although we need to improve the we need to improve the sample), suggesting a sample), suggesting a chemical relation. chemical relation.

(Vaduvescu, Richer & (Vaduvescu, Richer & McCall 2007)McCall 2007)

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Dwarf evolution in clustersDwarf evolution in clusters

To compare star forming galaxy isolated evolution (Local Volume To compare star forming galaxy isolated evolution (Local Volume d<10 Mpc) with the evolution of dwarf galaxies in nearby galaxy d<10 Mpc) with the evolution of dwarf galaxies in nearby galaxy clusters (d<100 Mpc) and higher redshift. clusters (d<100 Mpc) and higher redshift.

Virgo (14 Mpc)Virgo (14 Mpc) Fornax (17 Mpc)Fornax (17 Mpc) Hydra (49 Mpc)Hydra (49 Mpc) Antlia (35 Mpc)Antlia (35 Mpc) Perseus (5 Mpc)Perseus (5 Mpc) Abell 779 (92 Mpc)Abell 779 (92 Mpc) Abell 1367 (90 Mpc)Abell 1367 (90 Mpc) Others with WHT, GTC, etc. Others with WHT, GTC, etc.

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Dwarf evolution in clustersDwarf evolution in clusters

Compared with the LV Compared with the LV (isolated objects), star (isolated objects), star forming dwarfs in Virgo forming dwarfs in Virgo appear to obey the same appear to obey the same FP, FP, while Hydra appear to while Hydra appear to suffer some enviromental suffer some enviromental effects.effects.

Fornax sample is Fornax sample is insignificant for any insignificant for any conclusions, and needs conclusions, and needs increased. increased.

(Vaduvescu, Vilchez, (Vaduvescu, Vilchez, Kehrig, et al, 2011). Kehrig, et al, 2011).

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Dwarf evolution in clustersDwarf evolution in clusters

Apparently, the Apparently, the chemical evolution chemical evolution looks similar in Virgo, looks similar in Virgo, Fornax and Hydra, as Fornax and Hydra, as seen through the seen through the closed box model. closed box model.

New GMOS New GMOS spectroscopic data spectroscopic data was acquired recently was acquired recently in Antlia cluster. in Antlia cluster.

(Vaduvescu, Kehrig, (Vaduvescu, Kehrig, Smith-Castelli, Smith-Castelli, Richtler 2011 & 2012) Richtler 2011 & 2012) – in reduction. – in reduction.

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CollaboratorsCollaborators Prof. Marshall McCall, York Univ, Canada; Prof. Marshall McCall, York Univ, Canada; Dr. Robin Fingerhut, York Univ, Canada; Dr. Robin Fingerhut, York Univ, Canada; Dr. Michael Richer, OAN-SPM, Mexico; Dr. Michael Richer, OAN-SPM, Mexico;

Students Francisco Pozo and Angie Barr, UCN Chile -> Bochum Students Francisco Pozo and Angie Barr, UCN Chile -> Bochum

Univ; Univ; Prof. Dr. Eduardo Unda-Sanzana, UCN -> UA, Antofagasta, Chile; Prof. Dr. Eduardo Unda-Sanzana, UCN -> UA, Antofagasta, Chile; Dr. Marcus Albrecht, UCN -> Univ. Bonn, Germany; Dr. Marcus Albrecht, UCN -> Univ. Bonn, Germany; Dr. Analia Smith-Castelli, La Plata, Argentina; Dr. Analia Smith-Castelli, La Plata, Argentina; Dr. Lidia Makarova, SAO, Russia; Dr. Lidia Makarova, SAO, Russia;

Prof. Dr. Jose Vilchez, IAA, Granada, Spain; Prof. Dr. Jose Vilchez, IAA, Granada, Spain; Dr. Carolina Kehrig, IAA, Granada, Spain; Dr. Carolina Kehrig, IAA, Granada, Spain; Dr. Jorje Iglesias-Paramo, IAA, Granada, Spain; Dr. Jorje Iglesias-Paramo, IAA, Granada, Spain; Drd. Vasiliky Petropoulou, IAA, Granada, Spain; Drd. Vasiliky Petropoulou, IAA, Granada, Spain; Dr. Daniel Reverte, GTC La Palma. Dr. Daniel Reverte, GTC La Palma. 23

Future workFuture work

Improve the dwarf FP using new radio data (Paolo Serra + new HI Improve the dwarf FP using new radio data (Paolo Serra + new HI

surveys) and deeper NIR data to study further the phsyical link surveys) and deeper NIR data to study further the phsyical link

between dIs and BCDs; between dIs and BCDs;

Enlarge the dE NIR sample (Blanco 2009 run, Peletier collab, first Enlarge the dE NIR sample (Blanco 2009 run, Peletier collab, first

release of VISTA, etc) and study their relation with star forming release of VISTA, etc) and study their relation with star forming

dwarfs; dwarfs;

Approach the relation of our dwarf FP with other classic FPs for Approach the relation of our dwarf FP with other classic FPs for

giants, in the attempt to constraint their physical evolution. giants, in the attempt to constraint their physical evolution.

Due to my present busy support job and other science interests Due to my present busy support job and other science interests

(and also because I became a father!) I need students or collaborators (and also because I became a father!) I need students or collaborators

to continue these line of research. Eventually I could co-supervise one to continue these line of research. Eventually I could co-supervise one

PhD student together with another thesis director (from IAC, ULL or PhD student together with another thesis director (from IAC, ULL or

others from abroad). others from abroad).

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ReferencesReferences

Vaduvescu, O. and McCall, M., 2004, PASP 116, 640 Vaduvescu, O. and McCall, M., 2004, PASP 116, 640 Strategies for Imaging Faint Extended Sources in the Near-InfraredStrategies for Imaging Faint Extended Sources in the Near-Infrared

Vaduvescu, O. et al, 2005, AJ 130, 1593 Vaduvescu, O. et al, 2005, AJ 130, 1593 Infrared Properties of Star-Forming Dwarf Galaxies. I. Dwarf Irregular Galaxies Infrared Properties of Star-Forming Dwarf Galaxies. I. Dwarf Irregular Galaxies in the Local Volumein the Local Volume

Vaduvescu, O., Richer, M., and McCall, M., 2006, AJ 131, 1318 Vaduvescu, O., Richer, M., and McCall, M., 2006, AJ 131, 1318 Infrared Properties of Star-Forming Dwarf Galaxies. II. Blue Compact Dwarf Infrared Properties of Star-Forming Dwarf Galaxies. II. Blue Compact Dwarf Galaxies in the Virgo ClusterGalaxies in the Virgo Cluster

Vaduvescu, O. and McCall, M., 2005, Proc. IAU No. 198Vaduvescu, O. and McCall, M., 2005, Proc. IAU No. 198dEs and the dI fundamental planedEs and the dI fundamental plane

Vaduvescu, O., McCall, M. and Richer, M., 2007, AJ 134, 604 Vaduvescu, O., McCall, M. and Richer, M., 2007, AJ 134, 604 Chemical Properties of Star-Forming Dwarf GalaxiesChemical Properties of Star-Forming Dwarf Galaxies

Vaduvescu, O. and McCall, M., 2008, A&A 487, 147Vaduvescu, O. and McCall, M., 2008, A&A 487, 147The fundamental plane of dwarf irregular galaxiesThe fundamental plane of dwarf irregular galaxies

Vaduvescu, O., et al. 2011, A&A 553, 95Vaduvescu, O., et al. 2011, A&A 553, 95Searching for Star Forming Galaxies in Fornax and Hydra ClustersSearching for Star Forming Galaxies in Fornax and Hydra Clusters

McCall, M., Vaduvescu, O., et al. 2012, A&A 540, 49McCall, M., Vaduvescu, O., et al. 2012, A&A 540, 49Fundamentals of the Dwarf Fundamental PlaneFundamentals of the Dwarf Fundamental Plane

http://www.ovidiuv.ca/http://www.ovidiuv.ca/papers/papers/

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