On the origin of near-infrared extragalactic background light anisotropy

Abstract

Extragalactic background light (EBL) anisotropy traces variations in the total production of photons over cosmic history, and may contain faint, extended components missed in galaxy point source surveys. Infrared EBL fluctuations have been attributed to primordial galaxies and black holes at the epoch of reionization (EOR), or alternately, intra-halo light (IHL) from stars tidally stripped from their parent galaxies at low redshift. We report new EBL anisotropy measurements from a specialized sounding rocket experiment at 1.1 and 1.6 micrometers. The observed fluctuations exceed the amplitude from known galaxy populations, are inconsistent with EOR galaxies and black holes, and are largely explained by IHL emission. The measured fluctuations are associated with an EBL intensity that is comparable to the background from known galaxies measured through number counts, and therefore a substantial contribution to the energy contained in photons in the cosmos.At near-infrared wavelengths, where the large zodiacal light foreground complicates absolute photometry measurements, the extragalactic background light (EBL) may be best accessed by anisotropy measurements. On large angular scales, fluctuations are produced by the clustering of galaxies, which is driven by the underlying distribution of dark matter. EBL anisotropy measurements can probe emission from epoch of reionization (EOR) galaxies (1-3) and directcollapse black holes (4) that formed during the EOR before the universe was fully ionized by exploiting the distinctive Lyman cutoff feature in the rest-frame ultraviolet (UV), thus probing the UV luminosity density at high redshifts (5). However, large-scale fluctuations may also arise from the intrahalo light (IHL) created by stars stripped from their parent galaxies during tidal interactions (6) at redshift z < 3. A multi-wavelength fluctuation analysis can distinguish among these scenarios and constrain the EOR star formation rate.A search for such background components must carefully account for fluctuations produced 2 by known galaxy populations. Linear galaxy clustering is an important contribution to fluctuations on scales much larger than galaxies themselves. On fine scales, the variation in the number of galaxies produces predominantly Poissonian fluctuations, with an amplitude that depends on the luminosity distribution. Anisotropy measurements suppress foreground galaxy fluctuations by masking known galaxies from an external catalog.The first detections of infrared fluctuations in excess of the contribution from known galaxies with the Spitzer Space Telescope (7-9) were interpreted as arising from a population of faint first-light galaxies at z > 7. The Hubble Space Telescope was used at shorter wavelengths (10) to carry out a fluctuation study in a small deep field but did not report fluctuations in excess of known galaxy populations. Measurements with the AKARIsatellite (11) show excess fluctuations with a blue spectrum rapidly rising from 4.1μm to 2.4μm. Fluctuation measurements in a large survey fi...

Probing Large-scale Coherence between Spitzer IR and Chandra X-Ray Source-subtracted Cosmic Backgrounds

“…and Zemcov et al (2014) suggested that "orphan" stars at z ∼ 1 − 5 in a diffuse intrahalo light could fully explain the detected excess CIB fluctuation. Our measurement of the CIB vs CXB coherence means that intra-halo light could produce most of the CIB excess only if a substantial fraction (larger than that observed in galaxies) of the orphan stars are X-ray binaries or pulsars or share the same environment with hot X-ray emitting gas.…”

“…This Diffuse Galactic Light is very faint at 3.6 and 4.5 µm, and is generally estimated through extrapolation from, or cross correlation with, much brighter interstellar emission at other wavelengths (e.g., Kashlinsky et al 2005;Arendt et al 2010;Zemcov et al 2014;Matsumoto et al 2011;Seo et al 2015). Galactic X-rays also scatter in the diffuse ISM (Molaro et al 2014) and thus might correlate with the IR.…”

“…Its origin is debated: it can be attributed entirely to high-redshift sources Yue et al 2013) or to diffuse intra-halo light around galaxies at z = 1 − 5 Zemcov et al 2014) and (Kashlinsky 2017, for a review). At shorter wavelengths, not directly relevant to this study, the situation is less clear with conflicting measurements from 2MASS (Kashlinsky et al 2002;Odenwald et al 2003), NICMOS (Thompson et al 2007a,b) and CIBER (Zemcov et al 2014) as discussed in detail in Sec. 2.1.2 of Kashlinsky et al (2015).…”

Ligo Gravitational Wave Detection, Primordial Black Holes, and the Near-Ir Cosmic Infrared Background Anisotropies

“…Bird et al (2016) discuss how the observed detection rate, inferred from the so 4 We limit the range to where there is overall consistency between the CIB fluctuation results from various instruments (AKARI and Spitzer) and analyses. The situation at 1-1.6 μm is contradictory as discussed in detail in Kashlinsky et al (2015b, Section 2.1.2): conflicting levels have been measured by, on the one hand, the mutually consistent (at the same depth) deep 2MASS (Kashlinsky et al 2002;Odenwald et al 2003) and NICMOS (Thompson et al 2007a(Thompson et al , 2007b analyses and, on the other, the much shallower CIBER (Zemcov et al 2014) data. far single published event, can be made consistent with that expected from the PBHs making up the DM such that their comoving mean mass density, assumed constant since their formation until at least their possible later evolution (discussed in Section 4 and references therein), is given by Below we will assume, for simplicity, that all PBHs have identical mass.…”

Interstellar Extinction

“…And the unexpected discovery by the Cosmic Infrared Background ExpeRiment (CIBER) rocketborne experiment of powerful emission in the near IR from the peripheries of galaxies and from intergalactic space (Zemcov, et al (2014)) is evidently a manifestation of neglected fine dust. Thus, it is possible that up to now the spatial mass density of all dust (and not just the coarse dust) has been underestimated.…”