Wolf-Rayet Stars in IC10: Probing the Massive Star Content of the Nearest Starburst Wolf-Rayet Stars in IC10: Probing the Massive Star Content of the Nearest Starburst IC~10 is a Local Group galaxy currently undergoing a galaxy-wide starburst (Massey \& Armandroff 1995). Starburst galaxies have often been suspected of having a top-heavy IMF, although the evidence in general has been indirect (i.e., M82 according to Rieke et al.\ 1980). Previous work on the evolved massive star population of IC~10 suggested that it too might have a top-heavy IMF as evidenced by the relatively large ratio of WC-type to WN-type Wolf-Rayet stars. However, a newly completed survey has detected a wealth of new Wolf-Rayet candidates (Massey \& Holmes 2003). If these are spectroscopically confirmed as predominately of WN-type, the IMF of this starburst system may be normal, although the massive star population (and hence the amount of ``burst") may be factors of 5 higher than the already large value previously thought. IC~10 is the only starburst system sufficiently close to determine the massive star population {\it directly}, but it requires spectroscopy with Gemini-N and GMOS to take advantage of this unique opportunity. Starburst galaxies are undergoing intense star formation at a rate that is unsustainable on a Hubble time (e.g., Searle \& Sargent 1972). The nearest such object is the small irregular Local Group galaxy IC~10. Van den Bergh (2000) kindly credits the recognition of IC10's starburst nature to Massey \& Armandroff (1995), who identified $\sim 20$ Wolf-Rayet stars (WRs). WRs are the He-burning descendents of the most massive O-type stars, and this high number in such a small galaxy was considered quite remarkable; for comparison, NGC~6822, another Local Group irregular of comparable absolute visual magnitude contains only 4 WRs (Massey \& Johnson 1998). Other lines of evidence, such as the H$\alpha$ luminosity, also argue for a starburst nature (Hodge \& Lee 1990; Youngblood \& Hunter 1999; Hunter 2001). The galaxy is embedded in an extended H~I envelope (Huchtmeier 1979); presumably infalling gas fuels the burst. The proximity of IC~10 gives us a unique opportunity to study the effects that an intense burst has on the {\it process} of star formation, and in particular the slope of the stellar initial mass function (IMF). There has long been the theoretical expectation that the IMF would be be top-heavy in regions of intense star formation (Larson 1986). And, indeed such a claim has been made for the starburst galaxy M~82 (Rieke et al.\ 1980), based admittedly on fairly indirect evidence (see Scalo 1990 and Leitherer 1998). However, direct measurement of the IMF in the energetic central cluster (R136) of the 30 Dor giant HII region by Massey \& Hunter (1998) found a perfectly normal IMF. Stiil, there is evidence to suggest that IC~10 may in fact have a top-heavy IMF. Wolf-Rayet stars occur as two distinct types: those of the WN class, which show the products of H-burning at their surfaces, and those of the WC class, which show the products of He-burning at their surfaces. The mass range that is expected to evolve to WCs or WNs should be a function of metallicity (due to the effect that radiatively-driven stellar winds have on the evolution of massive stars) but at a given metallicity the WCs will {\it on average} be descended from more massive stars than are the WNs. (See discussion in Massey \& Johnson 1998 and Massey 2003). The WR stars found by Massey \& Armandroff (1995) were predominantly of WC type, unexpected in a galaxy of IC~10's low metallicity (Fig.~1). One explanation is that the IMF is more weighted in favor of massive stars in IC~10 due to its current starburst (Massey \& Armandroff 1995; Massey \& Johnson 1998). However, another possibility exists: WNs are more difficult to detect than WCs as their strongest emission lines are about a factor of 4 weaker than those of WCs, and thus completeness for WNs is much harder to achieve in any kind of a survey. (That is why the point for the Milky Way is also a bit high in Fig.~1---the sample there is probably not complete for WNs, as discussed in Massey 2003). IC10's low galactic latitude ($-3.3^\circ$) results in a large galactic foreground reddening ($E(B-V)=0.75-0.80$, according to Massey \& Armandroff 1995) further complicating detection. Accordingly, two years ago we proposed and were granted time on the 4-m Mayall to conduct a deeper imaging survey for WR stars using Mosaic and our ``optimized" interference filters centered on WR emission lines. Our survey has uncovered a wealth of additional candidates (Massey \& Holmes 2003; see also Crowther et al.\ 2003). By comparing the number of detections with those of a nearby control field, we conclude that the total number of WRs in IC10 might be as great as 100. If the majority of the new candidates are of WN-type (which might be expected if the stronger-lined WCs have mostly all been previously detected), then these new candidates could even lower the WC to WN ratio to normal---with the implication that the IMF is also normal. Of course, this would also imply that IC~10 is an even more extreme starburst than previously thought! So far, only two of these new candidates have been observed spectroscopically---both confirmed as WNs. To obtain a reasonably complete sample requires the large aperture of Gemini and the multiplexing capability of GMOS. \begin{figure} \epsscale{0.85} \plotone{N0163.01.eps} \caption{The relative number of WC and WN stars is well correlated with metallicity as we would expect; the exceptions are the Milky Way, and IC~10. The fact that the Milky Way ratio is high is easy to understand: the sample within 2.5~kpc is probably not complete for WNs. This figure has been adopted from Massey \& Johnson 1998, with the errors bars showing the effects of $\sqrt{N}$ statistics on the ratios.} \end{figure} \reference Armandroff, T. E., \& Massey, P. 1995, AJ, 109, 2470 \reference Crowther, P. et al.\ 2003, A\&A, 404, 483 \reference Hodge, P., \& Lee, M. G. 1990, PASP, 102, 1245 \reference Huchtmeier, W. K. 1979, A\&A, 75, 170 \reference Hunter, D. A. 2001, ApJ, 559, 225 \reference Larson, R. 1986, MNRAS, 218, 409 \reference Leitherer, C. 1998, in The Stellar Initial Mass Function, ed. G. Gilmore \& D. Howell, 61 \reference Massey, P. 2003, {\it ARA\&A}, 15, 41 \reference Massey, P. \& Holmes, S. 2002, ApJ, 580, L35 \reference Massey, P., \& Hunter, D. A. 1998, ApJ, 493, 180 \reference Massey, P., \& Johnson, O. 1998, ApJ, 505, 793 \reference Rieke, G. H., Lebofsky, M. J., Thompson, R. I., Low, F. J., \& Tokunaga, A. T. 1980, ApJ, 238, 24 \reference Scalo, J. M. 1990, in Windows on Galaxies, ed. A. Renzini, G. Gabbiano, \& J. S. Gallagher, 125 \reference Searle, L., \& Sargent, W. L. W. 1972, ApJ, 173, 25 \reference van den Bergh, S. 2000, The Galaxies of the Local Group \reference Youngblood, A. J., \& Hunter, D. A. 1999, ApJ, 519, 55 \begin{figure} \epsscale{0.75} \plotone{N0163.02.eps} \caption{This plot shows a simulation of the detection of He~II $\lambda 4686$ with parameters typical of a weak-lined WN stars; e.g., a line width of 20\AA\ and a equivalent width of -10\AA. The S/N per 0.9\AA (binned) pixel is indicated.} \end{figure} \clearpage NOAO PAST USE: {\bf Recent (2000-2003) allocation of time:} {\bf 2004A-200:} The Physical Parameters of Red Supergiants: When Massive Stars Are as Cool as They Get, 10 nights KPNO 2.1-m (5 successfully carried out in March, 5 more scheduled in late May), plus 5 nights CTIO 1.5-m scheduled for April. {\bf Target of Opportunity:} Spectroscopy of a Newly Found Dwarf Irregular, 2 hrs kindly granted by Richard Green on the 2.1-m with GoldCam, April 2003. The data appear in Massey, Henning, \& Kraan-Korteweg, 2003, AJ, 126, 2362 \relatedwork{{\bf 2002B-218:} The Evolution and Physical Parameters of Massive Stars at High Metallicity: O Stars in the Andromeda Galaxy", 3 nights MMT Sept 2002. We obtained only 0.5 nights out of 3 nights scheduled, due to weather, but published what we were able to get in Massey \& Holmes 2002, ApJ, 580, L35} {\bf 2001A-062:} A {\it UBVR} Survey of the Magellanic Clouds, 6 nights CTIO Curtis Schmidt April 2001: Massey 2002, ApJS 141, 81 \relatedwork{{\bf 2001B-002:} The Wolf-Rayet Content of IC10, 2 nights Mayall 4-m Sept 2001: Massey \& Holmes 2002, ApJ, 580, L35} {\bf 2001B-227:} The Red Supergiant Content of the Magellanic Clouds, 3 nights CTIO 4-m Hydra, October 2001. Massey \& Olsen 2003, AJ, 126, 2867 {\bf 2000B-010:} A Survey of Local Group Galaxies Currently Forming Stars, on-going survey project. We are current with all of our data reductions, and are completing the photometric analysis. Some data appear in Di Stefano et al. 2004, ApJ, in press (astroph-0306440) {\bf 1999B-099; 2000B-070:} Where Do Wolf-Rayet Stars Come From? CTIO 1.5-m 5 nights October 2000; 6 nights October 1999: Massey \& Duffy 2001, ApJ 550, 713; Niemela et al. 2002, MNRAS, 333, 347 \noindent {\bf Recent papers (2002-2004) based upon NOAO data:} \parindent=10pt Massey, P., Bresolin, F., Kudritzki, R. P., Puls, J., \& Pauldrach. A. W. A. ``The Effective Temperature Scale of O-type Stars as a Function of Metallicity. I. A Sample of 20 Stars in the Magellanic Clouds", ApJ, in press (June 20 issue, astroph/0402633) Walborn et al.\ 2004, ``A CNO Dicomotomy Among O2 Giant Spectra in the Magellanic Clouds", ApJ, in press (June 20 issue) Bianchi, L., Bohlin, R., \& Massey, P. 2003, ``The Ofpe/WN9 Stars in M33", ApJ, 601, 228 Massey, P. 2003, ``The Massive Star Content of the Local Group: Implications for Star Formation and Stellar Evolution", ARA\&A, 41, 15 Di Stefano et al. 2003, ``Supersoft X-Ray Sources in M31", ApJ, submitted, astro-ph/0306440 Massey, P., Olsen, K. A. G., \& Parker, J. W. 2003, ``The Discovery of a 12th Wolf-Rayet Star in the Small Magellanic Cloud", PASP, 115, 1265 astro-ph/0308237 Massey, P., Henning, P. A., \& Kraan-Korteweg, R. C. 2003, ``A Neighboring Dwarf Irregular Galaxy Hidden By the Milky Way", AJ 126, in press (Nov issue), astro-ph/0308080 Massey, P., \& Olsen, K. A. G. 2003, ``The Evolution of Massive Stars. I. Red Supergiants in the Magellanic Clouds", AJ, 126, 2867 astro-ph/0309272 Morrell, N. I., Ostrov, P. G., Massey, P., \& Gamen, R. 2003, ``Hodge 53-47: An Early O-type Double-lined Binary in the SMC", MNRAS, 341, 583 Massey, P., \& Holmes, S. 2002 ``Wolf-Rayet Stars in IC10: Probing the Nearest Starburst", ApJ 580, L35 Massey, P. 2002, ``A UBVR CCD Survey of the Magellanic Clouds," ApJS, 141, 81 Massey, P. 2002, ``Observational Constraints on Massive Star Evolution" (invited review), in {\it A Massive Star Odyssey, from Main Sequence to Supernova, IAU 212}, ed. van der Hucht, Herrero, \& Esteban, 316. Slesnick, C. L., Hillenbrand, L. A., \& Massey, P. 2002, ``The Star Formation History and Mass Function in the Double Cluster h and Chi Persei", ApJ, 576, 880 Snow, T. P., Zukowski, D., \& Massey, P. 2002, ``The Intrinsic Profile of the 4428\AA\ Diffuse Interstellar Band", ApJ 578, 877 Niemela, V. S., Massey, P., Testor, G., \& Benitez, S. G. 2002, ``The Massive Wolf-Rayet Binary WR7 in the SMC", MNRAS, 333, 347 Walborn et al. 2002, ``A Giant O2-O4 Spectral Classification Study", AJ, 123, 2754 Bianchi et al. 2001,``The Massive Star Content of NGC 6822. Ground-based and {\it HST} photometry, AJ, 121, 2020. Massey, P. \& Duffy, A. S. 2001, ``A Deep Search for Wolf-Rayet Stars in the Small Magellanic Cloud", ApJ, 550, 713. Massey, P., DeGioia-Eastwood, K., \& Waterhouse, E. 2001, ``The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turn-offs. II. Results from 12 Clusters in the Milky Way", AJ, 121, 1050. \parindent=0pt ***EXPERIMENTAL DESIGN***: With Gemini-N, we will obtain GMOS multi-slit observations of $\sim 30$ of our weaker-lined Wolf-Rayet candidates. The size of IC10 is a good match to the 5.5 arcmin diameter masks, and we can use a single slit mask. {\bf Time assigned for this project in 2003B resulted in obtaining a suitable image from which we designed a slit mask, but the spectroscopic data was never obtained.} For the spectroscopy we need reasonable resolution and S/N for a solid detection/non-detection: our WR candidates are faint ($B\sim 22-23$) and the expected emission of the strongest line (He~II $\lambda 4686$) weak (EWs of -10\AA; see Table 3 of Massey \& Johnson 1998 ApJ, 505, 793). The B600 grating offers 6\AA\ resolution (with a 1-arcsec slit), which is a good match to the width of the spectral lines (10-20\AA). We can bin by 2 pixels both spatially and spectrally, and as our simulation shows (Fig.~3), we require at least a S/N of 5 per 0.9\AA (binned) pixel for a convincing detection of such a line. According to the GEMINI GMOS exposure time calculator tool, we will achieve this S/N for a $B\sim 23$ object in a 5 hr exposure (20 x 900 sec) assuming dark skies (20 percentile) and mediocre seeing (80 percentile), using 1-arcsec wide slits. We will do the observation in two sets of 10x900 seconds, moving the central wavelength of the grating by 3nm to provide continuous wavelength coverage. As part of our survey of Local Group galaxies we also obtained imaging through our WR filters of {\it all} the Local Group galaxies currently active in forming stars: ten fields covering M31, 3 fields covering M33, plus single fields covering other Local Group galaxies. We view this IC~10 half-night as a test run for a more extensive proposal that will help identify the evolved massive star population (both red supergiants and WRs) in these nearby systems. \proprietaryperiod{18 months} ***TECHNICAL DESCRIPTION***: Dark time is needed as our objects are faint ($B\sim 23$) and the emission weak. The B600 grating provides good spectral coverage and adequate resolution, and the observations can be obtained in ``mediocre" (for Gemini!) seeing. As a 900-sec exposure will be photon-noise limited, we will combine 20 of these to obtain the equivalent of a 5-hr exposure. In the experimental design section we argue that a S/N of 5 per 0.9\AA\ spectral resolution element is needed for certain detection of emission in our weakest-lined cases (Fig.~2), and the GMOS ETC assures us we will achieve this with a 5-hr exposure under dark skies and 80-percentile seeing. We were granted Gemini-N time for this project in semester 2003B, and we obtained excellent imaging data under good seeing conditions that went quite deep enough to design a slitlet mask. But the spectroscopic observations were never made. The mask has been cut and is ready to go; we require only a half night (5-hr plus overhead) to complete this project. \geminidata{pcontactnum}{1} {\bf Principal Contact:} Philip Massey Comments from PI: None Program accepted for rollover into semester 05A and 05B if not completed in 04B. <html> <head><title>Phase 1 Proposal</title></head> <body bgcolor="#FFFFFF">  <a name="prolog"></a>  <a name="phase1Document"></a>  <a name="summary"></a> <table width="100%" cellspacing="10" border="0"> <tr><td align="center"><font size="+2"><b>GEMINI OBSERVATORY</b></font><br><i><font size="+1">observing time request (HTML summary)</font></i></td></tr> </table> <p> <p> <table width="100%" cellspacing="5" border="0"> <tr><td valign="top" colspan="2"><b>Semester: </b>2004B</td><td colspan="2"><b>Partner reference: </b><br>2004B0163R1</td><td><b>PI time requested: </b><br>6.0 hours</td></tr> <tr><td colspan="2"><b>Gemini reference: </b><br>GN-2004B-Q-12</td><td valign="top" colspan="2"><b>Partner ranking: </b>6</td><td><b>PI minimum time requested:</b><br>0.6 nights</td></tr> <tr><td colspan="2"><b>Instruments(s): </b><br>GMOS North</td><td colspan="2"><b>NTAC recommended time: </b><br>6.0 hours</td><td><b>PI future time requested: </b><br>0.0 nights</td></tr> <tr><td valign="top" colspan="2"><b>Observing mode: </b>queue</td><td colspan="2"><b>NTAC minimum recommended:</b><br>6.0 hours</td><td><b>PI total from all partners: </b>0.0 nights<br><i>(joint proposals)</i></td></tr> <tr><td colspan="2"><b>Time awarded: </b><br>6.0 hours</td><td><b>Proposal submitted to: </b>United States</td></tr> </table>  <a name="investigators"></a> <hr> <table cellspacing="5" width="100%" height="167" border="0"> <tr><td valign="top" height="38"><b>Title:</b></td><td height="38"><b>Wolf-Rayet Stars in IC10: Probing the Massive Star Content of the Nearest Starburst</b></td></tr> <tr><td><b>Principal Investigator:</b></td><td><b>Philip Massey</b></td></tr> <tr><td valign="top"><b>PI institution:</b></td><td>Lowell Observatory, 1400 W. Mars Hill Rd,Flagstaff, AZ 86001,USA</td></tr> <tr><td><b>PI status:</b></td><td>PhD/Doctorate</td></tr> <tr><td valign="top"><b>PI phone / fax / e-mail:</b></td><td>928-233-3264 / (928) 774-6296 / Phil.Massey@lowell.edu </td></tr> <tr><td><b>Principal Contact:</b></td><td><b>Philip Massey</b></td></tr> <tr><td valign="top"><b>PC institution:</b></td><td>Lowell Observatory</td></tr> <tr><td valign="top"><b>PC phone / fax / e-mail:</b></td><td>928-233-3264 / (928) 774-6296 / Phil.Massey@lowell.edu </td></tr> <tr><td valign="top"><b>Co-investigators:</b></td><td>Shadrian Holmes: Univ of Texas, sholmes@astro.as.utexas.edu </td></tr> </table>  <a name="abstract"></a> <hr> <h3></h3> <b>Abstract:</b> <i>IC~10 is a Local Group galaxy currently undergoing a galaxy-wide starburst (Massey \& Armandroff 1995). Starburst galaxies have often been suspected of having a top-heavy IMF, although the evidence in general has been indirect (i.e., M82 according to Rieke et al.\ 1980). Previous work on the evolved massive star population of IC~10 suggested that it too might have a top-heavy IMF as evidenced by the relatively large ratio of WC-type to WN-type Wolf-Rayet stars. However, a newly completed survey has detected a wealth of new Wolf-Rayet candidates (Massey \& Holmes 2003). If these are spectroscopically confirmed as predominately of WN-type, the IMF of this starburst system may be normal, although the massive star population (and hence the amount of ``burst") may be factors of 5 higher than the already large value previously thought. IC~10 is the only starburst system sufficiently close to determine the massive star population {\it directly}, but it requires spectroscopy with Gemini-N and GMOS to take advantage of this unique opportunity. </i>  <a name="scienceJustification"></a> <hr> <h3>Science Justification</h3> Starburst galaxies are undergoing intense star formation at a rate that is unsustainable on a Hubble time (e.g., Searle \& Sargent 1972). The nearest such object is the small irregular Local Group galaxy IC~10. Van den Bergh (2000) kindly credits the recognition of IC10's starburst nature to Massey \& Armandroff (1995), who identified $\sim 20$ Wolf-Rayet stars (WRs). WRs are the He-burning descendents of the most massive O-type stars, and this high number in such a small galaxy was considered quite remarkable; for comparison, NGC~6822, another Local Group irregular of comparable absolute visual magnitude contains only 4 WRs (Massey \& Johnson 1998). Other lines of evidence, such as the H$\alpha$ luminosity, also argue for a starburst nature (Hodge \& Lee 1990; Youngblood \& Hunter 1999; Hunter 2001). The galaxy is embedded in an extended H~I envelope (Huchtmeier 1979); presumably infalling gas fuels the burst. <p> The proximity of IC~10 gives us a unique opportunity to study the effects that an intense burst has on the {\it process} of star formation, and in particular the slope of the stellar initial mass function (IMF). There has long been the theoretical expectation that the IMF would be be top-heavy in regions of intense star formation (Larson 1986). And, indeed such a claim has been made for the starburst galaxy M~82 (Rieke et al.\ 1980), based admittedly on fairly indirect evidence (see Scalo 1990 and Leitherer 1998). However, direct measurement of the IMF in the energetic central cluster (R136) of the 30 Dor giant HII region by Massey \& Hunter (1998) found a perfectly normal IMF. <p> Stiil, there is evidence to suggest that IC~10 may in fact have a top-heavy IMF. Wolf-Rayet stars occur as two distinct types: those of the WN class, which show the products of H-burning at their surfaces, and those of the WC class, which show the products of He-burning at their surfaces. The mass range that is expected to evolve to WCs or WNs should be a function of metallicity (due to the effect that radiatively-driven stellar winds have on the evolution of massive stars) but at a given metallicity the WCs will {\it on average} be descended from more massive stars than are the WNs. (See discussion in Massey \& Johnson 1998 and Massey 2003). The WR stars found by Massey \& Armandroff (1995) were predominantly of WC type, unexpected in a galaxy of IC~10's low metallicity (Fig.~1). One explanation is that the IMF is more weighted in favor of massive stars in IC~10 due to its current starburst (Massey \& Armandroff 1995; Massey \& Johnson 1998). <p> However, another possibility exists: WNs are more difficult to detect than WCs as their strongest emission lines are about a factor of 4 weaker than those of WCs, and thus completeness for WNs is much harder to achieve in any kind of a survey. (That is why the point for the Milky Way is also a bit high in Fig.~1---the sample there is probably not complete for WNs, as discussed in Massey 2003). IC10's low galactic latitude ($-3.3^\circ$) results in a large galactic foreground reddening ($E(B-V)=0.75-0.80$, according to Massey \& Armandroff 1995) further complicating detection. Accordingly, two years ago we proposed and were granted time on the 4-m Mayall to conduct a deeper imaging survey for WR stars using Mosaic and our ``optimized" interference filters centered on WR emission lines. <p> Our survey has uncovered a wealth of additional candidates (Massey \& Holmes 2003; see also Crowther et al.\ 2003). By comparing the number of detections with those of a nearby control field, we conclude that the total number of WRs in IC10 might be as great as 100. If the majority of the new candidates are of WN-type (which might be expected if the stronger-lined WCs have mostly all been previously detected), then these new candidates could even lower the WC to WN ratio to normal---with the implication that the IMF is also normal. Of course, this would also imply that IC~10 is an even more extreme starburst than previously thought! So far, only two of these new candidates have been observed spectroscopically---both confirmed as WNs. To obtain a reasonably complete sample requires the large aperture of Gemini and the multiplexing capability of GMOS. <p> \begin{figure} \epsscale{0.85} \plotone{N0163.01.eps} \caption{The relative number of WC and WN stars is well correlated with metallicity as we would expect; the exceptions are the Milky Way, and IC~10. The fact that the Milky Way ratio is high is easy to understand: the sample within 2.5~kpc is probably not complete for WNs. This figure has been adopted from Massey \& Johnson 1998, with the errors bars showing the effects of $\sqrt{N}$ statistics on the ratios.} \end{figure} <p> \reference Armandroff, T. E., \& Massey, P. 1995, AJ, 109, 2470 \reference Crowther, P. et al.\ 2003, A\&A, 404, 483 \reference Hodge, P., \& Lee, M. G. 1990, PASP, 102, 1245 \reference Huchtmeier, W. K. 1979, A\&A, 75, 170 \reference Hunter, D. A. 2001, ApJ, 559, 225 \reference Larson, R. 1986, MNRAS, 218, 409 \reference Leitherer, C. 1998, in The Stellar Initial Mass Function, ed. G. Gilmore \& D. Howell, 61 \reference Massey, P. 2003, {\it ARA\&A}, 15, 41 \reference Massey, P. \& Holmes, S. 2002, ApJ, 580, L35 \reference Massey, P., \& Hunter, D. A. 1998, ApJ, 493, 180 \reference Massey, P., \& Johnson, O. 1998, ApJ, 505, 793 \reference Rieke, G. H., Lebofsky, M. J., Thompson, R. I., Low, F. J., \& Tokunaga, A. T. 1980, ApJ, 238, 24 \reference Scalo, J. M. 1990, in Windows on Galaxies, ed. A. Renzini, G. Gabbiano, \& J. S. Gallagher, 125 \reference Searle, L., \& Sargent, W. L. W. 1972, ApJ, 173, 25 \reference van den Bergh, S. 2000, The Galaxies of the Local Group \reference Youngblood, A. J., \& Hunter, D. A. 1999, ApJ, 519, 55 <p> \begin{figure} \epsscale{0.75} \plotone{N0163.02.eps} \caption{This plot shows a simulation of the detection of He~II $\lambda 4686$ with parameters typical of a weak-lined WN stars; e.g., a line width of 20\AA\ and a equivalent width of -10\AA. The S/N per 0.9\AA (binned) pixel is indicated.} \end{figure} <p> \clearpage <p> <h4>Attachments:</h4> <table width="100%" border="1"> <tr bgcolor="#4AA02C"><td><b>Name</b></td><td><b>Source</b></td><td><b>Type</b></td></tr> <tr><td>Science Justification</td><td>scijust.ps</td><td>PS</td></tr> </table>  <a name="technicalJustification"></a> <hr> <h3>Technical Justification</h3> ***EXPERIMENTAL DESIGN***: <p> With Gemini-N, we will obtain GMOS multi-slit observations of $\sim 30$ of our weaker-lined Wolf-Rayet candidates. The size of IC10 is a good match to the 5.5 arcmin diameter masks, and we can use a single slit mask. {\bf Time assigned for this project in 2003B resulted in obtaining a suitable image from which we designed a slit mask, but the spectroscopic data was never obtained.} <p> For the spectroscopy we need reasonable resolution and S/N for a solid detection/non-detection: our WR candidates are faint ($B\sim 22-23$) and the expected emission of the strongest line (He~II $\lambda 4686$) weak (EWs of -10\AA; see Table 3 of Massey \& Johnson 1998 ApJ, 505, 793). The B600 grating offers 6\AA\ resolution (with a 1-arcsec slit), which is a good match to the width of the spectral lines (10-20\AA). We can bin by 2 pixels both spatially and spectrally, and as our simulation shows (Fig.~3), we require at least a S/N of 5 per 0.9\AA (binned) pixel for a convincing detection of such a line. According to the GEMINI GMOS exposure time calculator tool, we will achieve this S/N for a $B\sim 23$ object in a 5 hr exposure (20 x 900 sec) assuming dark skies (20 percentile) and mediocre seeing (80 percentile), using 1-arcsec wide slits. We will do the observation in two sets of 10x900 seconds, moving the central wavelength of the grating by 3nm to provide continuous wavelength coverage. <p> As part of our survey of Local Group galaxies we also obtained imaging through our WR filters of {\it all} the Local Group galaxies currently active in forming stars: ten fields covering M31, 3 fields covering M33, plus single fields covering other Local Group galaxies. We view this IC~10 half-night as a test run for a more extensive proposal that will help identify the evolved massive star population (both red supergiants and WRs) in these nearby systems. <p> \proprietaryperiod{18 months} <p> ***TECHNICAL DESCRIPTION***: <p> Dark time is needed as our objects are faint ($B\sim 23$) and the emission weak. The B600 grating provides good spectral coverage and adequate resolution, and the observations can be obtained in ``mediocre" (for Gemini!) seeing. As a 900-sec exposure will be photon-noise limited, we will combine 20 of these to obtain the equivalent of a 5-hr exposure. In the experimental design section we argue that a S/N of 5 per 0.9\AA\ spectral resolution element is needed for certain detection of emission in our weakest-lined cases (Fig.~2), and the GMOS ETC assures us we will achieve this with a 5-hr exposure under dark skies and 80-percentile seeing. <p> We were granted Gemini-N time for this project in semester 2003B, and we obtained excellent imaging data under good seeing conditions that went quite deep enough to design a slitlet mask. But the spectroscopic observations were never made. The mask has been cut and is ready to go; we require only a half night (5-hr plus overhead) to complete this project. <p> \geminidata{pcontactnum}{1} {\bf Principal Contact:} Philip Massey <h4>Attachments:</h4> <table width="100%" border="1"> <tr bgcolor="#4AA02C"><td><b>Name</b></td><td><b>Source</b></td><td><b>Type</b></td></tr> <tr><td>Technical Justification</td><td>runinfo.ps</td><td>PS</td></tr> </table>  <a name="observationDetails"></a> <hr> <h3>Observation Details</h3> <table width="100%" border="1"> <tr bgcolor="#4AA02C"><td valign="top"><b>Observation</b></td><td valign="top"><b>RA</b></td><td valign="top"><b>Dec</b></td><td valign="top"><b>Brightness</b></td><td><b>Total Time</b><br><i>(including overheads)</i></td></tr> <tr><td><b>IC10</b></td><td>00:20:24.5</td><td>+59:17:30</td><td>23</td><td>300.0 minutes</td></tr><tr><td>     <b>pwfs1001_1</b> (wfs)</td><td>0:20:21.228</td><td>59:12:10.81</td><td>9.70 R</td><td>separation 5.34</td></tr><tr><td>     <b>pwfs1001_2</b> (wfs)</td><td>0:20:16.052</td><td>59:23:14.13</td><td>11.20 R</td><td>separation 5.84</td></tr><tr><td>     <b>iwfs1001_1</b> (oiwfs)</td><td>0:20:40.051</td><td>59:14:30.62</td><td>10.60 R</td><td>separation 3.59</td></tr><tr><td colspan="2">     <a href="#observingConditions">observing conditions:</a> Global Default</td><td colspan="3"><a href="#resources">resources:</a> GMOS North</td></tr> </table>  <a name="resources"></a> <p> <b>Resources</b> <ul><li>Gemini North<ul><li>GMOS North (GMOS North)<ul><li>Focal Plane Unit<ul><li>Custom Mask</ul><li>Disperser<ul><li>B600_G5303</ul></ul></ul></ul>  <a name="observingConditions"></a> <p> <b>Observing Conditions</b> <table width="100%" border="1"> <tr bgcolor="#4AA02C"><td><b>Name</b></td><td><b>Image Quality</b></td><td><b>Sky Background</b></td><td><b>Water Vapor</b></td><td><b>Cloud Cover</b></td></tr> <tr><td>Global Default</td><td>85%</td><td>20%</td><td>Any</td><td>70%</td></tr> </table>  <a name="schedulingInformation"></a> <p> <b>Scheduling Information:</b> <p> <b>Synchronous dates: </b> <p> <b>Optimal dates: </b> 2004/8/1-2004/11/30 <br> <b>Reason: </b> <p> <b>Impossible dates: </b> 2005/1/1-2005/1/31 <br> <b>Reason: </b> None  <a name="allocationCommitteeComments"></a> <hr> <h3>Allocation Committee Comments</h3> <h4>NTAC Comment</h4> Comments from PI: None <h4>ITAC Comment</h4> Program accepted for rollover into semester 05A and 05B if not completed in 04B. <p> <h4>Gemini Comment</h4> <p>  <a name="additionalInformation"></a> <hr> <h3>Additional Information</h3>  <a name="keywords"></a> <br> <b>Keyword Category: </b> Galactic <p> <b>Keywords: </b> Massive stars, Wolf-Rayet stars  <a name="publications"></a> <p> <b>Publications:</b> <ul><li>NOAO PAST USE: {\bf Recent (2000-2003) allocation of time:} {\bf 2004A-200:} The Physical Parameters of Red Supergiants: When Massive Stars Are as Cool as They Get, 10 nights KPNO 2.1-m (5 successfully carried out in March, 5 more scheduled in late May), plus 5 nights CTIO 1.5-m scheduled for April. {\bf Target of Opportunity:} Spectroscopy of a Newly Found Dwarf Irregular, 2 hrs kindly granted by Richard Green on the 2.1-m with GoldCam, April 2003. The data appear in Massey, Henning, \& Kraan-Korteweg, 2003, AJ, 126, 2362 \relatedwork{{\bf 2002B-218:} The Evolution and Physical Parameters of Massive Stars at High Metallicity: O Stars in the Andromeda Galaxy", 3 nights MMT Sept 2002. We obtained only 0.5 nights out of 3 nights scheduled, due to weather, but published what we were able to get in Massey \& Holmes 2002, ApJ, 580, L35} {\bf 2001A-062:} A {\it UBVR} Survey of the Magellanic Clouds, 6 nights CTIO Curtis Schmidt April 2001: Massey 2002, ApJS 141, 81 \relatedwork{{\bf 2001B-002:} The Wolf-Rayet Content of IC10, 2 nights Mayall 4-m Sept 2001: Massey \& Holmes 2002, ApJ, 580, L35} {\bf 2001B-227:} The Red Supergiant Content of the Magellanic Clouds, 3 nights CTIO 4-m Hydra, October 2001. Massey \& Olsen 2003, AJ, 126, 2867 {\bf 2000B-010:} A Survey of Local Group Galaxies Currently Forming Stars, on-going survey project. We are current with all of our data reductions, and are completing the photometric analysis. Some data appear in Di Stefano et al. 2004, ApJ, in press (astroph-0306440) {\bf 1999B-099; 2000B-070:} Where Do Wolf-Rayet Stars Come From? CTIO 1.5-m 5 nights October 2000; 6 nights October 1999: Massey \& Duffy 2001, ApJ 550, 713; Niemela et al. 2002, MNRAS, 333, 347 \noindent {\bf Recent papers (2002-2004) based upon NOAO data:} \parindent=10pt Massey, P., Bresolin, F., Kudritzki, R. P., Puls, J., \& Pauldrach. A. W. A. ``The Effective Temperature Scale of O-type Stars as a Function of Metallicity. I. A Sample of 20 Stars in the Magellanic Clouds", ApJ, in press (June 20 issue, astroph/0402633) Walborn et al.\ 2004, ``A CNO Dicomotomy Among O2 Giant Spectra in the Magellanic Clouds", ApJ, in press (June 20 issue) Bianchi, L., Bohlin, R., \& Massey, P. 2003, ``The Ofpe/WN9 Stars in M33", ApJ, 601, 228 Massey, P. 2003, ``The Massive Star Content of the Local Group: Implications for Star Formation and Stellar Evolution", ARA\&A, 41, 15 Di Stefano et al. 2003, ``Supersoft X-Ray Sources in M31", ApJ, submitted, astro-ph/0306440 Massey, P., Olsen, K. A. G., \& Parker, J. W. 2003, ``The Discovery of a 12th Wolf-Rayet Star in the Small Magellanic Cloud", PASP, 115, 1265 astro-ph/0308237 Massey, P., Henning, P. A., \& Kraan-Korteweg, R. C. 2003, ``A Neighboring Dwarf Irregular Galaxy Hidden By the Milky Way", AJ 126, in press (Nov issue), astro-ph/0308080 Massey, P., \& Olsen, K. A. G. 2003, ``The Evolution of Massive Stars. I. Red Supergiants in the Magellanic Clouds", AJ, 126, 2867 astro-ph/0309272 Morrell, N. I., Ostrov, P. G., Massey, P., \& Gamen, R. 2003, ``Hodge 53-47: An Early O-type Double-lined Binary in the SMC", MNRAS, 341, 583 Massey, P., \& Holmes, S. 2002 ``Wolf-Rayet Stars in IC10: Probing the Nearest Starburst", ApJ 580, L35 Massey, P. 2002, ``A UBVR CCD Survey of the Magellanic Clouds," ApJS, 141, 81 Massey, P. 2002, ``Observational Constraints on Massive Star Evolution" (invited review), in {\it A Massive Star Odyssey, from Main Sequence to Supernova, IAU 212}, ed. van der Hucht, Herrero, \& Esteban, 316. Slesnick, C. L., Hillenbrand, L. A., \& Massey, P. 2002, ``The Star Formation History and Mass Function in the Double Cluster h and Chi Persei", ApJ, 576, 880 Snow, T. P., Zukowski, D., \& Massey, P. 2002, ``The Intrinsic Profile of the 4428\AA\ Diffuse Interstellar Band", ApJ 578, 877 Niemela, V. S., Massey, P., Testor, G., \& Benitez, S. G. 2002, ``The Massive Wolf-Rayet Binary WR7 in the SMC", MNRAS, 333, 347 Walborn et al. 2002, ``A Giant O2-O4 Spectral Classification Study", AJ, 123, 2754 Bianchi et al. 2001,``The Massive Star Content of NGC 6822. Ground-based and {\it HST} photometry, AJ, 121, 2020. Massey, P. \& Duffy, A. S. 2001, ``A Deep Search for Wolf-Rayet Stars in the Small Magellanic Cloud", ApJ, 550, 713. Massey, P., DeGioia-Eastwood, K., \& Waterhouse, E. 2001, ``The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turn-offs. II. Results from 12 Clusters in the Milky Way", AJ, 121, 1050. \parindent=0pt</ul>  <a name="pastAllocations"></a>  <a name="proposalContents"></a> <hr> <h2>Proposal Contents</h2> <a href="#summary">Summary</a> <br> <a href="#investigators">Investigators</a> <br> <a href="#abstract">Abstract</a> <br> <a href="#scienceJustification">Science Justification</a> <br> <a href="#technicalJustification">Technical Justification</a> <br> <a href="#observationDetails">Observation Details</a> <br> <a href="#allocationCommitteeComments">Allocation Committee Comments</a> <br> <a href="#additionalInformation">Additional Information</a> <br>  <a name="coda"></a> </body> </html> This is the acquisition exposure for MOS mask GN2004BQ012-01. The rotator should be at 180 degrees, the same as for my pre-imaging data. MOS observation for GN2004BQ012-01. The observations are being done with a rotator angle of 180 degrees, the same as for the pre-imaging data. The sequence will consist of 5 exposures of 1800 sec each with the B600 grating centered at 525nm, followed by 5 exposures of 1800 sec each with the grating dithered to 500nm. 525.0 520.0 This is the placeholder for the baseline twilight exposure through mask GN2004BQ012-01 This is the placehold for the baseline CuAr exposures obtained with a center of 525nm and 500nm. 525.0 520.0