Post tag or hashtag

$tax_query = array(
	'relation' => 'OR',
	array(
		'taxonomy'         => 'post_tag',
		'terms'            => '$taxonomy',
		'field'            => 'slug',
	),
	array(
		'taxonomy'         => 'hashtag',
		'terms'            => '$taxonomy',
		'field'            => 'slug',
	),
);