GO2LF: Creating a Square Degree of HST+Spitzer Fields from a Newly-Approved 612-hour Spitzer Program

It was wonderful to hear on Thursday that the 612-hour Spitzer/IRAC proposal led by my collaborators Mauro Stefanon and Gabe Brammer (co-PIs) was successful. The proposal — and now successful program — is to add Spitzer 3.6 and 4.5 micron data to ~250 fields with deep HST data in at least 3 bands, including both 1.2 micron and 1.6 micron channels. The proposal should allow us to search for z~9-11 galaxies and low-mass stars (T/Y dwarfs) using an additional ~1100 arcmin**2 area. This is even more area than impressive programs like CANDELS possess.

Props are due to both Mauro and Gabe. This is the second year in a row Mauro has successfully led (PI’d) a >500-hour program with Spitzer; Mauro has been doing absolutely amazing work as a postdoc and the next year could be his most impressive yet! Actually all three postdocs I’m working with in Leiden are amazing. And, as for Gabe’s role, not only did he work alongside Mauro to develop the proposal but he basically put together an entire archive with the full set of HST pointings that exist with 1.6 micron data… The total area is now > 3.5 square degrees! Without this archive Gabe put together, the proposal would not have been possible!

And finally should not forget the important role of Adam Burgasser and Benne Holwerda — who put together the very exciting science case for low-mass stars and convinced us to obtain 4.5 micron data over our fields! And also the role of Ivo Labbe — whose photometric code will facilitate photometry over the full set of hst (+now Spitzer) fields.


Building a Cross-Disciplinary Community for Early/Mid-Career Academics in the Leiden/Amsterdam Areas

I’m trying my hand at helping to create a community in the Leiden/Amsterdam Areas for Early/Mid-Career Academics. The goal would be to provide a forum for a broad spectrum of academics to regularly come together to share experiences and to make friends in different areas of study. Gatherings would be at a beautiful location, likely alternating between Leiden and Amsterdam.

I’m not sure how the experiment will go, but I think it would be very interesting to build a cross-disciplinary community / friendship circle in the academic sphere. Many academics often feel alone in the challenges they face, and so creating a community of support could be very useful to us all.

Those of you in the Leiden/Amsterdam area who are starting, associate, or even young full professors are encouraged to sign up.

As the initiative proceeds, I will provide some personal reflections on what transpires.


Early/mid-career academics in the Leiden/Amsterdam Areas

Leiden, NL
15 Young Academics

This is a meetup for early to mid-career academics in the Amsterdam and Leiden areas.  The aim of this group is to provide a space for young academics to make friends with sim…

Check out this Meetup Group →

Exploring the z>~7 Universe with ALMA

In just the past day, ALMA TAC announced the results of its cycle 6 call for telescope proposals.    The oversubscription of telescope time with the facility has been such that the vast majority of proposals are not going to be successful and only a small fraction of the proposals are approved for execution at an A-ranking, the highest priority.

Amazingly again this cycle, the proposals my collaborators and I submitted to pursue redshift z>~7 science received high ratings, and four were approved for execution in cycle 6, three with an A-rating and one with a B-rating.   This was an improvement over our proposal results the previous year, with one A-rated program and two B-rated programs.

Our recent proposal success has been in distinct contrast to our performance in cycles 1 through 4 and has clearly owed to the remarkable success of just 1 hour of observations from a C-ranked ALMA program in cycle 3 led by Renske Smit, a previous PhD student.

This program resulted in the detection of bright [CII] emission from two galaxies at z~7, allowing for the determination of the redshift for the two sources and a measurement of rotation in the two sources.   The result has been published this year in Nature, by lead author Renske Smit in a remarkable effort.

Amazingly, the [CII] lines seen in the Smit+2018 sources were more luminous than seen in any other normal z~7 galaxies, suggesting that we should follow up a much larger sample of galaxies to search for similar lines therefore probing the redshifts, kinematics, and other properties of z~7 galaxies.

In the past two cycles, our small collaboration — driven significantly by highly innovative work by Renske Smit — has won telescope time with a diverse set of scientific goals.   These have included (1) pursuing larger samples of z~7-8 galaxies with [CII] detections (yielding redshifts, [CII] luminosities, and rough dynamical masses) and dust constraints, (2) reobserving a bright z~7 source with a known [CII] line at higher spatial resolution (for a thorough, detailed probe of the kinematic structure), and (3) probing other lines (i.e., [OIII], [NII]) in bright z~7 galaxies.

It is remarkable how dramatically a team’s success with telescope proposals can be transformed by just a single hour of ALMA time.

Keck MOSFIRE Time!

Today I just received news that the NASA Keck proposal that a PhD student (Leindert Boogaard) and I collaborated on with Dominik Riechers was successful, and we will therefore be able to use 0.5 nights of time on the Keck telescope to observe sources over the Hubble Ultra Deep Field (HUDF).    This is exciting since it means that the PhD student I (together with Paul van der Werf) have in Leiden will have the opportunity to make use of the amazing capabilities of the MOSFIRE instrument to observe massive star-forming galaxies in the HUDF to determine both their redshifts and other physical properties.

As NASA Keck time is available to the entire scientific community in the United States, the time is extremely competitive, and will only be awarded to the best scientific projects.   Fortunately, Leindert and I were able to collaborate with Dominik Riechers to put together an extremely compelling proposal.    Our proposal leveraged an incredible allocation of 150 hours of ALMA time given to the ASPECS project (PIs: Fabian Walter, Manuel Aravena, and Chris Carilli), the first extragalactic large program approved for ALMA.   The major aim of that program was to conduct a blind search for molecular gas in the Hubble Ultra Deep Field by looking for CO rotational lines in ALMA bands 3 and 6, in addition to probing far-IR emission from dust in distant galaxies.

The goal of our proposal was to detect the [OIII] and Halpha emission lines from z~2-4 galaxies with MOSFIRE to obtain a precise determination of the systemic redshifts of the targeted galaxies.   With precise systemic redshift measurements, it becomes possible to look for very low S/N CO line emission from lower mass z~2-4 galaxies in the ALMA data and also to perform stacking studies.   At the same time, the line measurements allow us to probe other physical properties of distant galaxies, e.g., such as metallicities, star formation rates, velocity offsets, etc.   The new data should therefore be of use for Leindert in writing one or more scientific manuscripts and will add to the science that will be done with 10 hours of KMOS data we are obtaining on an overlapping samples of sources.

All in all, the success of this proposal is welcome news and just adds to the huge amount of success Leindert Boogaard has already enjoyed as a PhD student in Leiden.   Not only does Leindert already have an accepted Astronomy & Astrophysics manuscript on the galaxy star forming main sequence in lower-mass galaxies to z~1, but also Leindert was able to almost single-handedly write a successful ALMA proposal in his first year as a PhD student.

In just his first 2 years as a PhD student, Leindert now knows how to reduce and pursue science with MUSE, KMOS, HST grism, and ALMA data.   In addition, Leindert is now writing several of the central scientific manuscripts for the ASPECS project, working closely with Fabian Walter, Roberto Decarli, Manuel Aravena, and Jorge Gonzalez, and is increasingly internationally known.   Like my first student in Leiden Renske Smit, Leindert is showing  remarkable early potential to be a scientist at the highest levels, and it has truly been a pleasure to collaborate with Paul van der Werf on his supervision.   It is because of students like Leindert that being a professor (and other challenges) are truly worthwhile.

Three Spitzer/IRAC Proposals Approved in Cycle 14


My collaborators and I were happy to hear news from the Spitzer Science Center that three of our cycle-14 Spitzer/IRAC proposals were successful.    One of these proposals was a continuation of previous cycle proposals on z~9-11 candidates found in pure-parallel HST data from the BoRG + HIPPIES programs and was led by my humble self.    The purpose of this proposal (and similar proposals in previous cycles) was to allow us to distinguish z~9-11 candidates from possible low-redshift (z~1-3) interlopers  that can be present in high-redshift selections.   We had been previously successful with these type of programs in cycles 12 and 13, first by myself and then in an amazing effort by Stephanie Bernard, and the current proposal continued that track record of success.

The second successful proposal was led by Mauro Stefanon, a talented postdoc in my team (and that of Jarle Brinchmann and Ivo Labbe).   The purpose of the proposal was to complete the deep (~30 hour) Spitzer/IRAC coverage over the ~2 square degree COSMOS / UltraVISTA field.   Mauro’s proposal, COMPLETE2, built on earlier proposals by Ivo Labbe and Karina Caputi for the ~2000-hour SMUVS program and ~1000-hour COMPLETE program.   Up to 1000 hours of observations were grant to Mauro for the COSMOS/UltraVISTA field, bringing the total integration time over the area to ~4000 hours.

Finally, the third successful proposal was led by Benne Holwerda, with the goal of obtaining  more sensitive Spitzer/IRAC observations of bright z~8 galaxies discovered over the BoRG program.    These bright z~8 galaxies were recently the subject of a newly submitted manuscript by Joanna Bridge.   The deeper Spitzer/IRAC observations would allow for a more accurate measurement of the strength in the [OIII] line in these galaxies, while also further confirming the individual sources in the sample as robust z~8 galaxies.   Benne’s proposal is particularly interesting because all of the bright z>~7 [OIII]-emitters identified by Guido Roberts Borsani have been found to show Lyman-alpha in emission (see here and here), motivating spectroscopic follow-up of the sample as well.   Benne Holwerda had worked as a postdoctoral fellow on my team in Leiden, but has now moved onto an associate professor position at the University of Louisville.

Amazing News Coverage of Discovered z=9.11 Galaxy

A good bit of my time this week was spent speaking to really intelligent and enthusiastic science writers about the new ALMA result in Nature, May 16, 2018, spectroscopically confirming the Zheng et al. 2012 MACS1149-JD  galaxy to lie at z=9.11.   While the true credit for this discovery deservedly goes to the scientists leading this letter to Nature, Takuyo Hashimoto and Nicolas Laporte, I was grateful to have had the opportunity to provide my own perspective on this discovery thanks to the News & Views article I wrote for Nature and as a result of 4 interviews I did with science writers on this result.

Below are some links to some excellent write-ups on the result (where I also provided feedback to the write up by interviews I did with the writers):

Sky & Telescope, Shannon Hall

Space.com article Chelsea Gold

Cosmosmagazine.com, Rick Lovett