Introduction

Evidence of large numbers of Wolf-Rayet (WR) stars in galaxies serves as a tracer of recent starbursts. The locations of WR stars indicate where star formation occurred $\lesssim$ 10 Myr ago and where OB stars of mass $\gtrsim$ 20 M$_{\sun}$ evolved to this state (e.g., Schaerer et al. 1999 and references therein). From the numbers and locations of such stars, one can determine the starburst properties and can study the kinematical and morphological impact the starburst has on the interstellar medium (ISM). Such studies are particularly important in dwarf irregular galaxies because of their low escape velocity ( $\sim100~{\rm km~s}^{-1}$; Drissen, Roy, & Moffat 1993). Because starburst galaxies have large star formation rates (e.g., log $\Sigma_{{\rm SFR}} \approx -0.8$ M$_{\sun}$ yr$^{-1}$ kpc$^{-2}$; Kennicutt 1998), the number of massive stars is enhanced. With the detection of massive WR stars in these disturbed systems, it is possible to correlate the morphology of the gas (both H I and H II) and the recent star formation history.

NGC 1569 is a nearby (D = 2.2$\pm$0.6 Mpc; Israel 1988) Im galaxy that has been well-studied over the last 20 years. Two prominent, stellar-like features are located at the center of this galaxy, which are thought to be super-star clusters (SSCs; cf. Prada, Greve, & McKeith 1994) formed in a starburst 2-10 Myr ago [González-Delgado et al.(1997)]. It is speculated that they will evolve into globular clusters. Recent results suggest that SSC A is two stellar clusters superimposed on one another [De Marchi et al.(1997)]. Identifying 45 clusters within NGC 1569, [Hunter et al.(2000)] determined their ages which range from 2 Myr to 1 Gyr, and they found a subconcentration of clusters, including SSC A, had an age of 4-5 Myr old.

From multiwavelength studies the gaseous morphology of NGC 1569 shows evidence of high supernovae activity. Several studies using optical interference-filter imagery of the ionized gas show evidence of an eruptive event which occurred in the galaxy's past [Hodge(1974),de Vaucouleurs, de Vaucouleurs, & Pence(1974),Waller(1991),Hunter, Hawley, & Gallagher(1993),Devost, Roy, & Drissen(1997)]. Kinematics of the ionized gas that were studied by [Tomita, Outa, & Saitou(1994)] showed the expanding gas moves at speeds from 10 to 100 km s$^{-1}$. Heckman et al. (1995) found that the optical filaments at distances of 2 kpc from the center of the galaxy are traveling over 200 km s$^{-1}$. In the infrared, [Hunter et al.(1989)] observed the dust radiating warmer at 60-155 $\mu$m, which is explained by the starburst's strong radiation field, than dust in similar, irregular galaxies. Radio observations also show relics of the eruptive starburst. Israel & de Bruyn (1988) deduced a high frequency cutoff at 8$\pm$1 GHz, which they attributed to a decrease in relativistic electron injection about 5 Myr ago. Observations of HI [Reakes(1980),Israel & van Driel(1990),Stil & Israel(1998)] revealed that the distribution of neutral hydrogen is a clumpy ridge or disk surrounded by arms which mimic the H$\alpha$ arms seen in the optical. An HI hole was detected surrounding the SSCs and was formed after the starburst [Israel & van Driel(1990)]. The distribution of the global CO emission is similar to the HI distribution [Young, Gallagher, & Hunter(1984)]. High resolution CO maps show large (compared to ones in the Galaxy) giant molecular clouds surrounding the SSC A HI hole [Taylor et al.(1999)]. Finally, ROSAT PSPC and HRI images show an extended soft X-ray component perpendicular to the major axis of the galaxy [Heckman et al.(1995),Stevens & Strickland(1998)]. ASCA images of a hard X-ray source inside NGC 1569 were interpreted as either low-mass X-ray binaries or young supernova remnants [Della Ceca et al.(1996)].

The consensus of these studies is that a starburst occurred approximately 10 Myr ago. This event (of unknown origin) produced SSC A and B. However, companions found around dwarf irregular systems are common (e.g., Taylor et al. 1995). Stil & Israel (1998) have found a 7$\times$10$^6$ M$_{\sun}$ companion 5 kpc from NGC 1569, which makes it a possible explanation for what triggered the starburst. There are large numbers of OB and/or WR stars in the two clusters and the surrounding field. Because of the numbers of massive stars and their rapid evolution (first giving rise to stellar winds and then supernovae), the galaxy underwent a pronounced kinematical and morphological change, even disruption, during the past several Myr. Evidence suggests that the supernova ejected material will escape the galaxy and will enrich the intergalactic medium.

Previously, evidence of WR stars in NGC 1569 came primarily from spectroscopic studies. Using this method, WR stars were located in the ring nebula to the far East in the galaxy [Drissen, Roy, & Moffat(1993)], in SSC A [González-Delgado et al.(1997)], and elsewhere within NGC 1569 [Ho, Filippenko, & Sargent(1995),Martin & Kennicutt(1997)]. However, [Kobulnicky & Skillman(1997; hereafter KS97)] found that most of the galaxy's He II $\lambda$4686 emission was nebular and their slit locations covered some of the regions where WR stars were previously detected. Ground-based narrow-band $\lambda4686$ filter imagery of NGC 1569 was attempted with little success in finding WR stars (e.g., one stellar knot with a light He II $\lambda4686$ excess; Drissen, Roy, & Moffat 1993).

With the improvement of spatial resolution of the Hubble Space Telescope over ground-based instruments, it is possible to study the morphology of the ionized gas with higher detail and locate weak stellar He II emission-line sources. In this paper, new HST WFPC2 F469N filter images are presented in an attempt to locate WR stellar activity and to confirm the previous WR detections. The observations and data reduction are presented in §2 with the basic results of that analysis given in §3. Discussion of the implications of our findings is given in §4. In §5 a summary of our findings and concluding remarks are made.