Showing papers by "Brian Babler published in 2004"
TL;DR: In this article, the extinction ratio between two filters, e.g. A(J)/A(K), is calculated from the color distributions of observed stars, and the mean values of the color excess ratios (A(λ)-A(k))/(A(J)-A (K)) are calculated from those measured ratios.
Abstract: We determine and tabulate A(lambda)/A(K), the wavelength dependence of interstellar extinction, in the Galactic plane for 1.25um
829 citations
University of Wisconsin-Madison1, Space Science Institute2, University of Maryland, College Park3, Boston University4, University of California, Berkeley5, University of Minnesota6, Ludwig Maximilian University of Munich7, University of Wyoming8, European Space Agency9, California Institute of Technology10
TL;DR: The luminous, massive star formation region RCW 49, located in the southern Galactic plane, was imaged with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope as part of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) program.
Abstract: The luminous, massive star formation region RCW 49, located in the southern Galactic plane, was imaged with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope as part of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) program. The IRAC bands contain polycyclic aromatic hydro- carbon (PAH) features at 3.3, 6.2, 7.7, and 8.6 � m, as well as the Brline. These features are the major contributors to the diffuse emission from RCW 49 in the IRAC bands. The Spitzer IRAC images show that the dust in RCW 49 is distributed in a network of fine filaments, pillars, knots, sharply defined boundaries, bubbles, and bow shocks. The regions immediately surrounding the ionizing star cluster and W-R stars are evacuated of dust by stellar winds and radiation. The IRAC images of RCW 49 suggest that the dust in RCW 49 has been sculpted by the winds and radiation from the embedded luminous stars in the inner 5 0 (inner � 6 pc) of the nebula. At projected angular radii �> 5 0 from the central ionizing cluster, the azimuthally averaged infrared intensity falls off as � � � 3 . Both high-resolution radio and mid-IR images suggest that the nebula is density bounded along its western boundary. The filamentary structure of the dust in RCW 49 suggests that the nebula has a small dust filling factor and, as a consequence, the entire nebula may be slightly density bounded to H-ionizing photons. Subject headingg astrochemistry — dust, extinction — H ii regions — infrared: ISM — ISM: lines and bands
113 citations
Space Science Institute1, University of Wisconsin-Madison2, University of Maryland, College Park3, Boston University4, University of California, Berkeley5, University of Minnesota6, Ludwig Maximilian University of Munich7, University of Wyoming8, European Space Research and Technology Centre9, California Institute of Technology10
TL;DR: A photometric comparison of the sources in RCW 49 to a similar area to its north finds that at least 300 stars brighter than 13th magnitude in band [3.6] have infrared excesses inconsistent with reddening due to foreground extinction.
Abstract: GLIMPSE imaging using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope indicates that star formation is ongoing in the RCW 9 giant H II region. A photometric comparison of the sources in RCW 49 to a similar area to its north finds that at least 300 stars brighter than 13th magnitude in band [3.6] have infrared excesses inconsistent with reddening due to foreground extinction. These are likely young stellar objects (YSOs) more massive than 2.5 M⊙, suggesting that thousands more low-mass stars are forming in this cloud. Some of the YSOs are massive (B stars) and therefore very young, suggesting that a new generation of star formation is occurring, possibly triggered by stellar winds and shocks generated by the older (2-3 Myr) central massive cluster. The Spitzer IRAC camera has proven to be ideally suited for distinguishing young stars from field stars, and the GLIMPSE survey of the Galactic plane will likely find thousands of new star formation regions.
95 citations
TL;DR: In this article, a previously unseen low-latitude rich star cluster near l=31.3 degrees, b=-0.1 corrected for extinction, and a luminosity of M_K ~ -10.3 at 3.1 kpc.
Abstract: Spitzer Space Telescope imaging as part of the Galactic Legacy Mid-Plane Survey Extraordinaire (GLIMPSE) reveals a previously unidentified low-latitude rich star cluster near l=31.3 degrees, b=-0.1 degrees. Near-infrared JHK' photometry from the Wyoming Infrared Observatory indicates an extinction of A_V ~ 15+/-3 mag for cluster members. Analysis of 13CO features along the same sightline suggests a probable kinematic distance of 3.1 -- 5.2 kpc. The new cluster has an angular diameter of ~1-2 pc, a total magnitude m_{K_0}=2.1 corrected for extinction, and a luminosity of M_K ~ -10.3 at 3.1 kpc. In contrast to young massive Galactic clusters with ages <100 Myr, the new cluster has no significant radio emission. Comparison to theoretical K-band luminosity functions indicates an age of at least several Gyr and a mass of at least 10^5 solar masses. Unlike known old open clusters, this new cluster lies in the inner Galaxy at R_{GC} ~ 6.1 kpc. We designate this object ``GLIMPSE-C01'' and classify it as a Milky Way globular cluster passing through the Galactic disk. We also identify a region of star formation and fan-shaped outflows from young stellar objects in the same field as the cluster. The cluster's passage through the Galactic molecular layer may have triggered this star formation activity.
40 citations
TL;DR: In this paper, the wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sight lines along with the Serkowski curve for all the sight lines, although the relationship between K and λmax may be different from that found in the Galaxy.
Abstract: The wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sight lines. Only one sight line had been measured previously. The globular clusters, S78, S150, S233, and Baade 327 were used as point sources to probe the interstellar dust in M31. The Serkowski law produces good fits for all the sight lines, although the relationship between K and λmax may be different from that found in the Galaxy. The results of this study imply that the slope K/λmax may be significantly larger in M31. The Serkowski curves are significantly narrower than those of the same λmax in the Galaxy and may require extreme modifications to the size distributions of silicate particles. The fits for the four sight lines reveal values of λmax ranging from 4800 to 5500 A. These are consistent with average values of λmax measured in the Galaxy and the Magellanic Clouds. The range measured for M31 corresponds to RV values of 2.7–3.1. The range in RV seen in the Galaxy is 2.5–5.5 implying, for this small sample, that the average size of interstellar grains in M31 is typically smaller than that seen for Galactic grains if the nature of the grains is the same. Also, the polarization efficiency for these sight lines is large, although some bias is expected since sight lines known to have significant interstellar polarization were selected for the sample.
13 citations
TL;DR: The wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sightlines along with one sightline had been measured previously as mentioned in this paper, and the Serkowski curves are significantly narrower than those of the same lambda(max) in the Galaxy and may require extreme modifications to the size distributions of silicate particles.
Abstract: The wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sightlines Only one sightline had been measured previouslyThe globular clusters, S78, S150, S233 and Baade 327 were used as point sources to probe the interstellar dust in M31 The Serkowski law produces good fits for all the sightlines although the relationship between K and lambda(max) may be different from that found in the Galaxy The results of this study imply that the slope K/lambda(max) may be significantly larger in M31 The Serkowski curves are significantly narrower than those of the same lambda(max) in the Galaxy and may require extreme modifications to the size distributions of silicate particles The fits for the four sightlines reveal values of lambda(max) ranging from 4800 to 5500 A These are consistent with average values of lambda(max) measured in the Galaxy and the Magellanic Clouds The range measured for M31 corresponds to R(V) values of 27 to 31 The range in R(V) seen in the Galaxy is 25 to 55 implying, for this small sample, that the average size ofinterstellar grains in M31 is typically smaller than that seen for Galactic grains if the nature of the grains is the same Also, the polarization efficiency for these sightlines is large although some bias is expected since sightlines known to have significant interstellar polarization were selected for the sample
8 citations
Boston University1, University of Wisconsin-Madison2, Space Science Institute3, University of Maryland, College Park4, University of Wisconsin–Whitewater5, University of California, Berkeley6, University of Minnesota7, University of Wyoming8, European Space Research and Technology Centre9, California Institute of Technology10
TL;DR: In this paper, the authors used early, in-orbit checkout (IOC) images of a portion of the Galactic plane obtained by the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope revealed the presence of an extended emission nebula with internal structure.
Abstract: Examination of early, in-orbit checkout (IOC) images of a portion of the Galactic plane obtained by the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope revealed the presence of an extended emission nebula with internal structure. The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) data show this nebula, located at l � 42 � and b � 0N5, contains bright point sources and two nonstellar regions. Ancillary data sets were used to help reveal the nature of this nebula and its exciting objects. In particular, 13 CO J ¼ 1 ! 0 line emission mapped by the Galactic Ring Survey (GRS) shows molecular gas associated with the infrared nebula. The 13 CO radial velocity yields a far-kinematic distance of 11.1 kpc to the nebula, since there is no evidence for H i self-absorption. At 11.1 kpc, the far-infrared luminosity of the nebula is 4:8;10 4 L� , and the mass of its molecular cloud is 1:1;10 4 M� . The spectral energy distribution rises steeply from 2.2 to 100 � m with an absorption feature at 10 � m, exhibiting the shape of a late Class 0 young stellar object (YSO). The radio continuum flux observed toward the nebula is consistent with the free-free emission from one or more massive YSOs (MYSOs) with spectral types in the range O9 to B0. This analysis demonstrates one technique the GLIMPSE team will use for revealing thousands of Galactic star formation regions.
8 citations
Space Science Institute1, University of Wisconsin-Madison2, University of Maryland, College Park3, Boston University4, University of California, Berkeley5, University of Minnesota6, Ludwig Maximilian University of Munich7, University of Wyoming8, European Space Research and Technology Centre9, California Institute of Technology10
TL;DR: A photometric comparison of the sources in RCW 49 to a similar area to its north finds that at least 300 stars brighter than 13th magnitude in band [3.6] have infrared excesses inconsistent with reddening due to foreground extinction as mentioned in this paper.
Abstract: GLIMPSE imaging using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope indicates that star formation is ongoing in the RCW 49 giant H II region. A photometric comparison of the sources in RCW 49 to a similar area to its north finds that at least 300 stars brighter than 13th magnitude in band [3.6] have infrared excesses inconsistent with reddening due to foreground extinction. These are likely young stellar objects (YSOs) more massive than 2.5 M_sun suggesting that thousands more low-mass stars are forming in this cloud. Some of the YSOs are massive (B stars) and therefore very young, suggesting that a new generation of star formation is occurring, possibly triggered by stellar winds and shocks generated by the older (2-3 Myr) central massive cluster. The Spitzer IRAC camera has proven to be ideally suited for distinguishing young stars from field stars, and the GLIMPSE survey of the Galactic Plane will likely find thousands of new star formation regions.
3 citations