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 (D
Mpc, 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 (D
Mpc, Gieren et al.2005) and
M81 (D
Mpc, 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 (D
Mpc, Gieren et al.2006),
NGC2403 (D
Mpc, Saha et al.2006),
NGC0247 (D
Mpc, Madore et al.2009) and
NGC7793 (D
Mpc, 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 3.6
m
images of the targeted galaxies.
In what follows, we describe our methodology
(Section2) and present the point-source catalogs
(Section3).