Massive Stars in the

Interstellar Medium of

1613IC

Rebecca B. JerveyLycoming CollegeSummer 2004 REU

University of Wisconsin – Madison

IC 1613 IC 1613

Our Region in IC 1613

Dwarf Irregular GalaxyLocal Group (~730 kpc)Discovered in 1906 by WolfResolved into 17-18 magnitude stars by Bade and classified as Magellenic- Cloud type galaxy in 1928

Type O and B starsForm in clusters (“associations”)Massive so have short lifetimesEnd lives in supernovae

Energy Calculations

˚Stars emit energy (luminosity)˚This energy takes the shape of stellar winds˚Winds sweep up gas and dust creating bubbles˚As star continues to dump energy into the system the bubbles expand˚This process continues until the star explodes˚Supernovae release a sudden burst of energy

ºThis energy also sweeps out bubblesºLittle to no nearby gas after the stellar windsºSupernova bubbles travel fasterºIt catches up with the stellar wind bubbleºThe interaction between the bubbles heats the gas and dust up causing it to emit energy in the x-ray spectrum

QuickTimeª and aYUV420 codec decompressor

are needed to see this picture.

The energy from the supernovae and massive stars with be released according to the chart below. Some of this energy will then go into making stars like those on the right.

Stars forming in IC1396 due to high energy gas bubbles from supernovae

Photometry: Standard Stars

PG 0231+051 (Landolt 2000) Area 92 (Landolt 2000)

Standard Stars are stars which have been defined by acceptable meansLandolt (2000) is one catalogue of such starsOur observations were taken at Kitt Peak on the 3.5mm WIYN telescope but we don't yet know how that data relates to the standard systemTo calibrate our observations we first had to find the standard stars in our picturesThen we could compute reasonable calibration equations to relate the starsu=U + Constant + Color Term x (U-B) + Extinction x AirmassFrom here we were ready to look at stars with unknown quantities

Photometry: Crowded Field with daophot

Decide what is a starDo photometry to locate the stars that qualifyDetermine the Point Spread Function (PSF)Remove stars to find any that are hiddenDo photometry again on those starsCombine the photometry runsTransform into standard system using calibration equations (remember those?)

IC 1613 through the B filter

IC 1613 through the V filter

It is now time to actually analyze the stars. We now have the required information to find their ages and from there we can calculate the amount of energy they have blown off over their lifetimes.

Next: IRAF and SuperMongo

*Use SuperMongo to graph the text file from IRAF*Get a (V,B-V) diagram*Convert to Color Magnitude diagram using the distance modulus*Distance Modulus (m-M) = 24.27 ± 0.1*Add isochrones from Padua Library (Bertelli 1994)

*Locate OB associations based on Borissova (2003)*Determine number of stars in associations*Plot individual associations with isochrones*Determine ages of associations

Where we are now:

�Trying to fit the associations to isochrones�Determining their ages�Plugging the number of stars of each age back into the C++

program�Finding the energy that has been produced over the lifetimes of the

now existing stars

Calculating energy that has been produced by supernovaeCalculating energy that has been / is being used by star forming regionsPredicting that the excess energy is used in the heating of gas which

will emit in the x-ray spectrumWriting a Chandra proposal to view IC 1613 in the x-ray spectrumActually viewing IC 1613 in the x-ray spectrum and collecting dataAnalysing the data collectedFiguring out how much energy went into producing the x-raysChecking to see if our numbers match and if not trying to figure out

why

What's still to come:

A few things I learned this summer:

C++ JAVAHTML

SuperMongoIRAF

Photometry techniques

Irregular Galaxies

Supernovae

Stellar Feedback

And some cool places we went:

Fermilab

Yerkes Observatory

SRC

The Terrace State Street

University of Wisconsin-Madison

University of Wisconsin-MadisonResearch Experience for Undergraduates... in Astrophysics

Acknowledgments

I would like to thank Dr. Eric Wilcots for advising me in this project.

Thanks also go to Dr. Bob Benjamin and Dr. Christer Watson for being the REU contact people.

I thank the University of Wisconsin-Madison for providing us with a good location to both do research and live for the summer.

Also, the NSF deserves thanks for their funding and supporting REU programs everywhere.

Finally, I would like to thank all of you for your attention and helpful comments, criticisms, or questions you might have.

Thank You!

References

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Cole, A. A., et all 1999 AJ 118 1657-1670

Ferrara, A. and Tolstoy, E. 2000, MNRAS 313, 291-309

Goldberg, H. S. and Scadron, M. D. 1981, Physics of Stellar Evolution and Cosmology. (New York: Gordon and

Breach, Science Publishers, Inc.)

Hodge, P. W. 1978 APJS 37, 145-167

Hodge, P. W. 1980 APJ 241, 125-131

Kippenhahn, R. and Weigert, A. 1990, Stellar Structure and Evolution.  (Berlin:Springer-Verlag)

Lamers, H. J. G. L. M., and Cassinelli, J. P. 1999, Introduction to Stellar Winds(Cambridge: Cambridge University

Press)

Lamers, H. J. G. L. M. and Leitherer, C. 1993, APJ 412, 771-791

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Timmes, F.X. and Woosley, S.E. 1997, APJ 481, L81-L84

Vesperini, E. and Heggie, D. C. 1997, MNRAS 289, 898-920

Walter, F. 1999, The Violent Interstellar Medium of Dwarf Irregular Galaxies. (Germany: Shaker Verlag)

Wilcots, E. M. and Thurow, J. C. 2001, APJ 555, 758-774.

Yungelson, L. R. and Livio, M. 2000 APJ 528, 108-117