jQuery - draggable images on iPad / iPhone - how to integrate event.preventDefault();?

I use jQuery, jQuery UI and jQuery mobile to build a web application for iPhone / iPad. Now I create images and they should be draggable, so I did this:

Here you can see the live example: http://jsbin.com/igena4/

The problem is, that the whole page want to scroll. I searched in Apple's HTML5 examples and found this to prevent the scrolling of the page, so that the image is draggable:

...
onDragStart: function(event) {
    // stop page from panning on iPhone/iPad - we're moving a note, not the page
    event.preventDefault();
    ...
}

But the problem is for me, how can I include this into my jQuery? Where do I get event?

Best Regards.