On the abundance of gravitational arcs produced by submillimeter galaxies at radio and submm wavelengths

Abstract

We predict the abundance of giant gravitational arcs produced by submillimeter galaxies (SMGs) lensed by foreground galaxy clusters, both at radio and submm wavelengths. The galaxy cluster population is modeled in a realistic way with the use of semi-analytic merger trees, while the density profiles of individual deflectors take into account ellipticity and substructures. The adopted typical size of the radio and submm emitting regions of SMGs is based on current radio/CO observations and the FIR-radio correlation. The source redshift distribution has been modeled using three different functions (based on spectroscopic/photometric redshift measurements and a simple evolutionary model) to quantify the effect of a high redshift tail on the number of arcs. The source number counts are compatible with currently available observations, and were suitably distorted to take into account the lensing magnification bias. We present tables and plots for the numbers of radio and submm arcs produced by SMGs as a function of surface brightness, useful for the planning of future surveys aimed at arc statistics studies. They show that e.g., the detection of several hundred submm arcs on the whole sky with a signal-to-noise ratio of at least 5 requires a sensitivity of 1 mJy arcsec −2 at 850 μm. Approximately the same number of radio arcs should be detected with the same signal-to-noise ratio with a surface brightness threshold of 20 μJy arcsec −2 at 1.4 GHz. Comparisons of these results with previous work found in the literature are also discussed.

IDCS J1426.5+3508: COSMOLOGICAL IMPLICATIONS OF A MASSIVE, STRONG LENSING CLUSTER ATz= 1.75

“…We adopt the redshift distribution and number counts for sources in the Hubble Ultra Deep Field (UDF) provided by Coe et al (2006) for F775W and F160W, and correct the number counts for the lensing magnification bias using the same procedure detailed in Fedeli et al (2008) and Fedeli & Berciano Alba (2009). For the practical computation of the optical depth, we use the strategy detailed in Fedeli et al (2008) and references therein.…”

“…Briefly, merger trees are constructed based on the extended Press & Schechter (1974) theory, which represent a model of the cluster population. A lensing potential ellipticity is assigned to each cluster, extracted from the distribution shown in Fedeli & Berciano Alba (2009), and cluster dynamical activity occurring at the knots of the merger trees is suitably modeled. Individual clusters are modeled as NFW profiles with the assigned potential ellipticity, and the concentration is linked to the mass through the Gao et al (2008) prescription for the concentration, consistent with Section 4.2.…”

The final candidate from the JVAS/CLASS search for 6-15 arcsec image separation lensing

“…The prospects of carrying out surveys for radio emitting star‐forming galaxies behind clusters have become more appealing with the advent of new or upgraded radio facilities (see previous work by Garrett, Knudsen & van der Werf 2005; Berciano Alba et al 2010). Simulations by Fedeli & Berciano Alba (2009) find that over the whole sky, several 100 cluster lens systems could potentially be found from deep radio observations (∼20 μJy arcsec −2 surface‐brightness sensitivity at 1.4 GHz) that are within the sensitivity limits of, for example, the Expanded VLA.…”

Arc Statistics

“…This topic is discussed in a paper by Fedeli and Berciano Alba (2009). As pointed out by Blain (1996Blain ( , 1997, the fraction of lensed sources observed in the mm/submm wavebands is expected to be much larger than in the optical.…”

“…This effect, together with the steep slope of the observed submm number counts, produces a strong magnification bias that makes submm galaxies an ideal source population for the production of lensed arcs. Fedeli and Berciano Alba (2009) estimated that a submm all-sky survey with a sensitivity of 1 mJy arcsec −2 will detect hundreds of arcs with a 5σ significance. In the radio, this number can be achieved with a sensitivity of 10-20 µJy arcsec −2 .…”