By Sarah McBride and Yasmeen Abutaleb

STANFORD, Calif (Reuters) - Facebook Inc <FB.O> Chief Operating Officer Sheryl Sandberg re-emerged in public on Tuesday after the accidental death of her husband last week, offering a personal tribute to him in a Silicon Valley memorial service and on her Facebook page.
             
Many of the tech world's top executives filled a 1,700-seat auditorium at Stanford University to commemorate David Goldberg, chief executive of SurveyMonkey. He died at age 47 on Friday after a treadmill accident during a vacation in Mexico. 
             
"We had 11 truly joyful years of the deepest love, happiest marriage, and truest partnership that I could imagine," Sandberg posted on Facebook. "He gave me the experience of being deeply understood, truly supported and completely and utterly loved - and I will carry that with me always." 
             
Her post appeared hours after the ceremony, a tribute to the low-key executive, whose marriage to Sandberg added to his fame from building a company valued at $2 billion.
             
Speakers described Goldberg's self-deprecation, modesty and selflessness, and the event, closed to the media, included several nods to his passions.
             
On their way out, guests were offered Minnesota Vikings baseball caps as a reminder of the Minneapolis-born Goldberg's lighthearted nature and love of sports, according to a person who attended the service and who declined to be identified.
             
Also on hand were playing cards stamped with his initials, and poker chips. During the ceremony, U2’s Bono sang "One," the Irish rock band’s anthem to love and support.
             
Goldberg's brother, Robert Goldberg, who announced the death on Saturday morning on Facebook, and several friends spoke at the private service, the person said.   
             
Many guests entered through side and back doors after driving into a cordoned-off area behind the hall. Some, such as Hewlett Packard Chief Executive Meg Whitman, walked up the steps and through the main entrance. 
             
Many began offering personal tributes to Goldberg on social media on Saturday, including Facebook Chief Executive Mark Zuckerberg. Sandberg, however, remained silent until Tuesday morning, when she responded to a public note by President Barack Obama. 
             
"David Goldberg embodied the definition of a real leader - someone who was always looking for ways to empower others," the president wrote in a Facebook message signed B.O., meaning he personally wrote it. "We're heartbroken by him leaving us far too soon - but we celebrate a remarkable legacy." 
             
Sandberg in turn took to Facebook, thanking Obama for his friendship. "Dave Goldberg admired you for your leadership, passion, and your deep love of sports," she wrote.
             
She also changed her Facebook cover photo on Tuesday morning to a picture of her dancing with Goldberg at their wedding in 2004. 
             
Goldberg built SurveyMonkey into a poll-taking juggernaut after joining the company in 2009. He previously worked for venture firm Benchmark, after founding Launch Media and selling it to Yahoo Inc <YHOO.O> in 2001.
             
"As we put the love of my life to rest today, we buried only his body," Sandberg wrote. "His spirit, his soul, his amazing ability to give is still with it."
              
(Additional reporting by Yasmeen Abutaleb, Editing by Peter Henderson, Richard Chang and Ken Wills)