Further multiwavelength observations of the SSA22 Ly_alpha emitting `blob'

We present new follow-up observations of the sub-mm luminous Ly_alpha-emitting object in the SSA22 z=3.09 galaxy overdensity, referred to as `Blob 1' by Steidel et al.(2000). In particular we discuss high resolution Hubble Space Telescope optical imaging, Owens Valley Radio Observatory spectral imaging, Keck spectroscopy, VLA 20cm radio continuum imaging, and Chandra X-ray observations. We also present a more complete analysis of the existing James Clerk Maxwell Telescope sub-mm data. We detect several optical continuum components which may be associated with the core of the submillimeter emitting region. A radio source at the position of one of the HST components (22:17:25.94, +00:12:38.9) identifies it as the likely counterpart to the submillimeter source. We also tentatively detect the CO(4-3) molecular line, centered on the radio position. We use the CO(4-3) intensity to estimate a limit on the gas mass for the system. The optical morphology of sources within the Ly_alpha cloud appears to be filamentary, while the optical source identified with the radio source has a dense knot which may be an AGN or compact starburst. We obtain a Keck-LRIS spectrum of this object, despite its faintness (R=26.8). The spectrum reveals weak Ly_alpha emission, but no other obvious features, suggesting that the source is not an energetic AGN (or that it is extremely obscured). We use non-detections in deep Chandra X-ray images to constrain the nature of the `Blob'. Although conclusive evidence regarding the nature of the object remains hard to obtain at this redshift, the evidence presented here is at least consistent with a dust-obscured AGN surrounded by a starburst situated at the heart of this giant Ly_alpha cloud.Comment: 8 pages, 9figs (low res), to appear in ApJ, for higher res figures, http://www.submm.caltech.edu/~schapman/sa22_sept4.ps.g

AzTEC Millimetre Survey of the COSMOS Field - II. Source Count Overdensity and Correlations with Large-Scale Structure

We report an over-density of bright sub-millimetre galaxies (SMGs) in the 0.15 sq. deg. AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z <~ 1.1. This portion of the COSMOS field shows a ~ 3-sigma over-density of robust SMG detections when compared to a background, or "blankfield", population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG over-density is most significant in the number of very bright detections (14 sources with measured fluxes S(1.1mm) > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities and infers an over-density significance of >> 4. We find that the over-density and spatial correlation to optical-IR galaxy density are most consistent with lensing of a background SMG population by foreground mass structures along the line of sight, rather than physical association of the SMGs with the z <~ 1.1 galaxies/clusters. The SMG positions are only weakly correlated with weak-lensing maps, suggesting that the dominant sources of correlation are individual galaxies and the more tenuous structures in the region and not the massive and compact clusters. These results highlight the important roles cosmic variance and large-scale structure can play in the study of SMGs.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in MNRA

Presentations of Finitely Generated Cancellative Commutative Monoids and Nonnegative Solutions of Systems of Linear Equations

Varying methods exist for computing a presentation of a finitely generated commutative cancellative monoid. We use an algorithm of Contejean and Devie [An efficient incremental algorithm for solving systems of linear diophantine equations, Inform. and Comput. 113 (1994) 143–172] to show how these presentations can be obtained from the nonnegative integer solutions to a linear system of equations. We later introduce an alternate algorithm to show how such a presentation can be efficiently computed from an integer basis

Spitzer and near-infrared observations of a new bi-polar protostellar outflow in the Rosette Molecular Cloud

We present and discuss \emph{Spitzer} and near-infrared H$_{2}$ observations of a new bi-polar protostellar outflow in the Rosette Molecular Cloud. The outflow is seen in all four IRAC bands and partially as diffuse emission in the MIPS 24 $\mu$m band. An embedded MIPS 24 $\mu$m source bisects the outflow and appears to be the driving source. This source is coincident with a dark patch seen in absorption in the 8 $\mu$m IRAC image. \emph{Spitzer} IRAC color analysis of the shocked emission was performed from which thermal and column density maps of the outflow were constructed. Narrow-band near-infrared (NIR) images of the flow reveal H$_2$ emission features coincident with the high temperature regions of the outflow. This outflow has now been given the designation MHO 1321 due to the detection of NIR H$_2$ features. We use these data and maps to probe the physical conditions and structure of the flow.Comment: Accepted for publication in The Astrophysical Journa

On the Number of Factorizations of an Element in an Atomic Monoid

Let S be a reduced commutative cancellative atomic monoid. If s is a nonzero element of S, then we explore problems related to the computation of η(s), which represents the number of distinct irreducible factorizations of s∈S. In particular, if S is a saturated submonoid of Nd, then we provide an algorithm for computing the positive integer r(s) for which 0 \u3c limn→∞η(sn)nr(s)-1∞. We further show that r(s) is constant on the Archimedean components of S. We apply the algorithm to show how to compute limn→∞η(sn)nr(s)-1 and also consider various stability conditions studied earlier for Krull monoids with finite divisor class group

Density Variations in the NW Star Stream of M31

The Pan Andromeda Archeological Survey (PAndAS) CFHT Megaprime survey of the M31-M33 system has found a star stream which extends about 120 kpc NW from the center of M31. The great length of the stream, and the likelihood that it does not significantly intersect the disk of M31, means that it is unusually well suited for a measurement of stream gaps and clumps along its length as a test for the predicted thousands of dark matter sub-halos. The main result of this paper is that the density of the stream varies between zero and about three times the mean along its length on scales of 2 to 20 kpc. The probability that the variations are random fluctuations in the star density is less than 10^-5. As a control sample we search for density variations at precisely the same location in stars with metallicity higher than the stream, [Fe/H]=[0, -0.5] and find no variations above the expected shot noise. The lumpiness of the stream is not compatible with a low mass star stream in a smooth galactic potential, nor is it readily compatible with the disturbance caused by the visible M31 satellite galaxies. The stream's density variations appear to be consistent with the effects of a large population of steep mass function dark matter sub-halos, such as found in LCDM simulations, acting on an approximately 10Gyr old star stream. The effects of a single set of halo substructure realizations are shown for illustration, reserving a statistical comparison for another study.Comment: ApJ revised version submitte

Submillimeter Observations of the Ultraluminous BAL Quasar APM 08279+5255

With an inferred bolometric luminosity of 5\times10^{15}{\rm \lsun}, the recently identified z=3.87, broad absorption line quasar APM 08279+5255 is apparently the most luminous object currently known. As half of its prodigious emission occurs in the infrared, APM 08279+5255 also represents the most extreme example of an Ultraluminous Infrared Galaxy. Here, we present new submillimeter observations of this phenomenal object; while indicating that a vast quantity of dust is present, these data prove to be incompatible with current models of emission mechanisms and reprocessing in ultraluminous systems. The influence of gravitational lensing upon these models is considered and we find that while the emission from the central continuum emitting region may be significantly enhanced, lensing induced magnification cannot easily reconcile the models with observations. We conclude that further modeling, including the effects of any differential magnification is required to explain the observed emission from APM 08279+5255.Comment: 12 Pages with Two figures. Accepted for publication in the Astrophysical Journal Letter

Genesis of the dusty Universe: modeling submillimetre source counts

We model the evolution of IR galaxies using a phenomenological approach to match the observed source counts at different IR wavelengths. We introduce a new algorithm for reproducing source counts based on direct integration of probability distributions rather than Monte-Carlo sampling. We construct a simple model for the evolution of the luminosity function and the colour distribution of IR galaxies which utilizes a minimum number of free parameters. Moreover we analyze how each of these parameters is constrained by observational data. The model is based on pure luminosity evolution and adopts the Dale & Helou SED templates. We find that the 850um source counts and their redshift distribution depend strongly on the shape of the luminosity evolution function, but only weakly on the details of the SEDs. We derive the best-fit evolutionary model using the 850um counts and redshift distribution as constraints. Moreover our best-fit shows a flattening of the faint end of the luminosity function towards high redshifts and requires a colour evolution which implies the typical dust temperatures of objects with the same luminosities to decrease with redshift. We compare our best-fit model to observed source counts at shorter and longer wavelengths which indicates our model reproduces the 70um and 1100um source counts remarkably well, but under-produces the counts at intermediate wavelengths. Analysis reveals that the discrepancy arises at low redshifts, indicating that revision of the adopted SED library towards lower dust temperatures (at a fixed infrared luminosity) is required. This modification is equivalent to a population of cold galaxies existing at low redshifts, as also indicated by recent Herschel results, which are underrepresented in IRAS sample. We show that the modified model successfully reproduces the source counts in a wide range of IR and submm wavelengths.Comment: 21 pages, 11 figures, 2 tables. Accepted for publication in MNRAS. Supplementary information could be found at http://www.strw.leidenuniv.nl/genesis