HELP: xid+, the probabilistic de-blender forHerschelSPIRE maps

Abstract

We have developed a new prior-based source extraction tool, XID+, to carry out photometry in the Herschel SPIRE maps at the positions of known sources. XID+ is developed using a probabilistic Bayesian framework which 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. We show that not only does XID+ perform better on metrics such as flux accuracy and flux uncertainty accuracy, we 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 Her-MES, using a 24 µm catalogue as a prior and show the marginalised SPIRE colourcolour plot and marginalised 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 utilised. 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.

A Spectroscopic Follow-up Program of Very Massive Galaxies at 3 < z < 4: Confirmation of Spectroscopic Redshifts, and a High Fraction of Powerful AGNs

“…Figure 6 shows the observed far-infrared (FIR) SEDs of our targets with significant MIPS 24 μm detections. We include the Herschel PACS 100 and 160 μm photometry from the PACS Evolutionary Probe (PEP) survey DR1 public data release 9 Magnelli et al 2013) and Herschel SPIRE 250, 350, and 500 μm photometry from the Herschel Multi-tiered Extragalactic Survey (HerMES) DR3/4 public data release 10 (Roseboom et al Oliver et al 2012;Hurley et al 2017). These fluxes are listed in Table 4.…”

“Super-deblended” Dust Emission in Galaxies. I. The GOODS-North Catalog and the Cosmic Star Formation Rate Density out to Redshift 6

“…They tested their technique with a simulated PACS 160μm image and demonstrated such an approach can obtain reliable fluxes below the nominal confusion limit. Hurley et al (2017) developed a similar MCMC-based prior-extraction tool XID + , which can fit all prior sources to obtain the posterior PDF of the flux of each prior source. Then they measured SPIRE fluxes for COSMOS 24μm prior sources, tiling the full image into diamond-shaped regions to save computational resources.…”

An Application of Multi-band Forced Photometry to One Square Degree of SERVS: Accurate Photometric Redshifts and Implications for Future Science

“…These include software packages that use prior information from a band with high-resolution imaging to model the flux in lower-resolution bands such as T-PHOT (the successor to TFIT; Merlin et al 2015Merlin et al , 2016b, PyGFIT (Mancone et al 2013), XID+ (Hurley et al 2017), and other applications of Bayesian cross-matching (Marquez et al 2014;Budavári & Basu 2016), LAMDAR (Wright et al 2016), and The Tractor (Lang et al 2016a(Lang et al , 2016b. Each of these tools has different strengths and weaknesses in areas such as the available options for modeling sources (point-source/resolved surface brightness profile versus elliptical aperture), fitting heuristics (maximum likelihood estimator versus Bayesian inference), point-spread function (PSF) characterization (single Gaussian/mixture of Gaussians versus model image), algorithm speed, and accessibility to the user community.…”