Jillian M. Scudder

HELP: XID+, The Probabilistic De-blender for Herschel SPIRE maps

We have developed a new prior-based source extraction tool, xid+, to carry out photometry in the Herschel SPIRE (Spectral and Photometric Imaging Receiver) maps at the positions of known sources. xid+ is developed using a probabilistic Bayesian framework that provides a natural framework in which to include prior information, and uses the Bayesian inference tool Stan to obtain the full posterior probability distribution on flux estimates. In this paper, we discuss the details of xid+ and demonstrate the basic capabilities and performance by running it on simulated SPIRE maps resembling the COSMOS field, and comparing to the current prior-based source extraction tool desphot. Not only we show that xid+ performs better on metrics such as flux accuracy and flux uncertainty accuracy, but we also illustrate how obtaining the posterior probability distribution can help overcome some of the issues inherent with maximum-likelihood-based source extraction routines. We run xid+ on the COSMOS SPIRE maps from Herschel Multi-Tiered Extragalactic Survey using a 24-μm catalogue as a positional prior, and a uniform flux prior ranging from 0.01 to 1000 mJy. We show the marginalized SPIRE colour–colour plot and marginalized contribution to the cosmic infrared background at the SPIRE wavelengths. xid+ is a core tool arising from the Herschel Extragalactic Legacy Project (HELP) and we discuss how additional work within HELP providing prior information on fluxes can and will be utilized. The software is available at https://github.com/H-E-L-P/XID_plus. We also provide the data product for COSMOS. We believe this is the first time that the full posterior probability of galaxy photometry has been provided as a data product.

The multiplicity of 250- μm Herschel sources in the COSMOS field

We investigate the multiplicity of extragalactic sources detected by the Herschel Space Observatory in the COSMOS field. Using 3.6- and 24-μm catalogues, in conjunction with 250-μm data from Herschel, we seek to determine if a significant fraction of Herschel sources are composed of multiple components emitting at 250 μm.We use the XID+ code, using Bayesian inference methods to produce probability distributions of the possible contributions to the observed 250-μm flux for each potential component. The fraction of Herschel flux assigned to the brightest component is highest for sources with total 250-μm fluxes <45 mJy; however, the flux in the brightest component is still highest in the brightest Herschel sources. The faintest 250-μm sources (30–45 mJy) have the majority of their flux assigned to a single bright component; the second brightest component is typically significantly weaker, and contains the remainder of the 250-μm source flux. At the highest 250-μm fluxes (45–110 mJy), the brightest and second brightest components are assigned roughly equal fluxes, and together are insufficient to reach 100 per cent of the 250-μm source flux. This indicates that additional components are required, beyond the brightest two components, to reproduce the observed flux. 95 per cent of the sources in our sample have a second component that contains more than 10 per cent of the total source flux. Particularly for the brightest Herschel sources, assigning the total flux to a single source may overestimate the flux contributed by around 150 per cent.

HELP: star formation as a function of galaxy environment with Herschel

The Herschel Extragalactic Legacy Project (HELP) brings together a vast range of data from many astronomical observatories. Its main focus is on the Herschel data, which maps dust obscured star formation over 1300 deg2. With this unprecedented combination of data sets, it is possible to investigate how the star formation vs stellar mass relation (main-sequence) of star-forming galaxies depends on environment. In this pilot study we explore this question between 0:1 2. We also estimate the evolution of the star formation rate density in the COSMOS field and our results are consistent with previous measurements at z 2 but we find a 1:4 (superscript) +0:3 (subscript) 0:2 times higher peak value of the star formation rate density at z about 1:9.

Galaxy pairs in the SDSS - XIII. The connection between enhanced star formation and molecular gas properties in galaxy mergers

We investigate the connection between star formation and molecular gas properties in galaxy mergers at low redshift (z

Red, redder, reddest : SCUBA-2 imaging of colour-selected Herschel sources.

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JINGLE, a JCMT legacy survey of dust and gas for galaxy evolution studies : I. Survey overview and first results

0.06). The study we present is based on IRAM 30-m CO(1-0) observations of 11 galaxies with a close companion selected from the Sloan Digital Sky Survey (SDSS). The pairs have mass ratios

Cosmic happenstance: 24-µm selected, multicomponent Herschel sources are line-of-sight projections

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HELP: star formation as function of galaxy environmentwith Herschel

4, projected separations r

HELP: star formation as function of galaxy environment with Herschel

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Erratum : "HerMES : ALMA imaging of Herschel-selected dusty star-forming galaxies" (2015, ApJ, 812, 43).

30 kpc and velocity separations