The Spitzer Space Telescope (Spitzer, Werner et al.2004) enabled mid-infrared (mid-IR) observations with unprecedented sensitivity. An enormous archive of imaging data has been collected using the Infrared Array Camera (IRAC, Fazio et al.2004) and the Multiband Imaging Photometer (MIPS, Rieke et al.2004) instruments aboard Spitzer that have been utilized to study astrophysical objects in the Galaxy (e.g., Benjamin et al.2003) and beyond. In particular, Spitzer made it possible to study resolved stellar populations in the Magellanic Clouds (Gordon et al.2011; Meixner et al.2006; Bolatto et al.2007) and local group galaxies such as M31 (Mould et al.2008; Barmby et al.2006) and M33 (Thompson et al.2009; McQuinn et al.2007) in the mid-IR.
Although global galaxy properties beyond the local group have been extensively studied using Spitzer images (Willner et al.2004; Helou et al.2004), efforts to catalog individual mid-IR luminous sources in these galaxies have been limited. There are a number of sources of archival Spitzer data for nearby galaxies. The Spitzer Infrared Nearby Galaxies Survey (SINGS, Kennicutt et al.2003) made a comprehensive mid-IR imaging and spectroscopic survey of 75 galaxies, many of them within Mpc. The Local Volume Legacy Survey (LVL, Dale et al.2009) surveyed a total of 256 nearby galaxies, including all known galaxies inside a sub-volume bounded by Mpc and an unbiased sample of S-Irr galaxies within a larger, and more representative, Mpc sphere. The Spitzer Survey of Stellar Structure in Galaxies (, Sheth et al.2008) collected data for galaxies within Mpc using the warm Spitzer ( and ) bands.
While it is difficult to identify and characterize mid-IR point-sources in the crowded and dusty disks of large star forming galaxies due to IR emission from interstellar dust, blending and background contamination, it is possible to catalog mid-IR luminous stars in galaxies well beyond the Milky Way and the Magellanic clouds (Khan et al.2010; Thompson et al.2009; Gerke & Kochanek2013; Khan et al.2011). In Khan et al. (2013), we used archival IRAC images of seven galaxies (Mpc; closest to farthest: NGC, M, NGC, NGC, M, NGC, and NGC) in a pilot study to search for extragalactic analogs of the Galactic object Carinae, taking advantage of the data made available by the SINGS and LVL projects, which led to the identification of an emerging class of evolved massive ( ) stars (Khan et al.2015).
Here we present photometric inventories of the mid-IR point-sources in the IRAC , , , and MIPS images of the galaxies studied by Khan et al. (2013); Khan et al. (2015). Although we concentrated on galaxies with recent star formation, as only these would have large numbers of the short-lived, very massive stars that were our primary targets, we also included the small, low-mass galaxy NGC6822 as a test for examining large numbers of smaller, lower-metallicity systems. M33 (DMpc, Bonanos et al.2006) was previously cataloged by McQuinn et al. (2007) in the IRAC , and bands, and by Thompson et al. (2009) in the IRAC and bands. Point-sources in NGC300 (DMpc, Gieren et al.2005) and M81 (DMpc, Gerke et al.2011) were cataloged by Khan et al. (2010) in the IRAC and bands. The catalogs presented in this paper identify a larger number of sources in these galaxies than the previous studies. Spitzer point-source catalogs of NGC6822 (DMpc, Gieren et al.2006), NGC2403 (DMpc, Saha et al.2006), NGC0247 (DMpc, Madore et al.2009) and NGC7793 (DMpc, Tully et al.2009) are being published here for the first time.
We use the same datasets that were utilized by Khan et al. (2013); Khan et al. (2015). For M33, we use the six co-added epochs of IRAC data from McQuinn et al. (2007), and the MIPS data retrieved from the Spitzer Heritage Archive. For NGC300 and NGC247, we used the data from the LVL survey (Dale et al.2009). For NGC6822, NGC2403, M81, and NGC7793, we used the data from the SINGS survey (Kennicutt et al.2003). We utilize the full mosaics available for each galaxy. Figure 1 shows the IRAC 3.6m images of the targeted galaxies. In what follows, we describe our methodology (Section2) and present the point-source catalogs (Section3).