The notes are not tied. This is relatively conventional notation for portato, which is rather like a "sticky" staccato with longer but still detached notes.
Although not all engravers make the distinction, it is common to place ties and slurs differently. A tie should be placed between the note heads, while slurs should be placed conspicuously above or below them. In this case, the curved marking is quite conspiciously above the note heads, implying that it is a slur even though the pitch doesn't change.