A simultaneous search for High-$z$ LAEs and LBGs in the SHARDS survey
  We have undertaken a comprehensive search for both Lyman Alpha Emitters
(LAEs) and Lyman Break Galaxies (LBGs) in the SHARDS Survey of the GOODS-N
field. SHARDS is a deep imaging survey, made with the 10.4 m Gran Telescopio
Canarias (GTC), employing 25 medium band filters in the range from 500 to 941
nm. This is the first time that both LAEs and LBGs are surveyed simultaneously
in a systematic way in a large field. We draw a sample of 1558 sources; 528 of
them are LAEs. Most of the sources (1434) show rest-frame UV continua. A
minority of them (124) are pure LAEs with virtually no continuum detected in
SHARDS. We study these sources from $z\sim3.35$ up to $z\sim6.8$, well into the
epoch of reionization. Note that surveys done with just one or two narrow band
filters lack the possibility to spot the rest-frame UV continuum present in
most of our LAEs. We derive redshifts, Star Formation Rates (SFRs), Ly$\alpha$
Equivalent Widths (EWs) and Luminosity Functions (LFs). Grouping within our
sample is also studied, finding 92 pairs or small groups of galaxies at the
same redshift separated by less than 60 comoving kpc. In addition, we relate 87
and 55 UV-selected objects with two known overdensities at $z=4.05$ and
$z=5.198$, respectively. Finally, we show that surveys made with broad band
filters are prone to introduce many unwanted sources ($\sim20$% interlopers),
which means that previous studies may be overestimating the calculated LFs,
specially at the faint end.
