TOWARDS ROBUST LEARNING USING DIAMETRICAL RISK MINIMIZATION FOR NETWORK INTRUSION DETECTION

Currently, deep neural networks (DNNs) show great promise in the detection of malicious network traffic at machine speed. However, these networks are typically trained using Empirical Risk Minimization (ERM), which is not robust to misclassified or altered training data. We propose applying Diametrical Risk Minimization (DRM), which is shown to lead to more robust optimization solutions, to train DNNs to classify malicious network traffic. Using two different network traffic datasets, we find that when state-of-the-art DNNs are trained on partially mislabeled data, utilizing DRM results in higher accuracy compared to equivalent models trained with ERM in 13 of 20 cases examined, with ERM being more accurate in only 5 of the 20 cases. More importantly, when models are tested against previously unseen cyber-attack types, models trained with DRM correctly identify the previously unseen cyber-attacks more often. Of the 46 cases we examine, models trained with DRM show better performance compared to models trained with ERM in 25 cases and equal performance in an additional 10 cases. We show that these DNNs are computationally tractable to deploy in real-time on edge computing systems utilizing commercial-off-the-shelf hardware.Approved for public release. Distribution is unlimited.Outstanding ThesisCaptain, United States Marine Corp

Charting the evolution of the ages and metallicities of massive galaxies since z=0.7

The stellar populations of intermediate-redshift galaxies can shed light onto the growth of massive galaxies in the last 8 billion years. We perform deep, multi-object rest-frame optical spectroscopy with IMACS/Magellan of ~70 galaxies in the E-CDFS with redshift 0.6522.7 and stellar mass >10^{10}Msun. Following the Bayesian approach adopted for previous low-redshift studies, we constrain the stellar mass, mean stellar age and stellar metallicity of individual galaxies from stellar absorption features. We characterize for the first time the dependence of stellar metallicity and age on stellar mass at z~0.7 for all galaxies and for quiescent and star-forming galaxies separately. These relations for the whole sample have a similar shape as the z=0.1 SDSS analog, but are shifted by -0.28 dex in age and by -0.13 dex in metallicity, at odds with simple passive evolution. We find that no additional star formation and chemical enrichment are required for z=0.7 quiescent galaxies to evolve into the present-day quiescent population. However, this must be accompanied by the quenching of a fraction of z=0.7 Mstar>10^{11}Msun star-forming galaxies with metallicities comparable to those of quiescent galaxies, thus increasing the scatter in age without affecting the metallicity distribution. However rapid quenching of the entire population of massive star-forming galaxies at z=0.7 would be inconsistent with the age/metallicity--mass relation for the population as a whole and with the metallicity distribution of star-forming galaxies only, which are on average 0.12 dex less metal-rich than their local counterparts. This indicates chemical enrichment until the present in at least a fraction of the z=0.7 massive star-forming galaxies.[abridged]Comment: accepted for publication on ApJ, 26 pages, 13 figure

On the Reported Death of the MACHO Era

We present radial velocity measurements of four wide halo binary candidates from the sample in Chaname & Gould (2004; CG04) which, to date, is the only sample containing a large number of such candidates. The four candidates that we have observed have projected separations >0.1 pc, and include the two widest binaries from the sample, with separations of 0.45 and 1.1 pc. We confirm that three of the four CG04 candidates are genuine, including the one with the largest separation. The fourth candidate, however, is spurious at the 5-sigma level. In the light of these measurements we re-examine the implications for MACHO models of the Galactic halo. Our analysis casts doubt on what MACHO constraints can be drawn from the existing sample of wide halo binaries.Comment: 6 Pages, 4 Figures, Accepted for MNRAS Letter

On the Binary Nature of Dust-encircled BD+20 307

Three epochs of high resolution spectra of the star BD+20 307 show that it is a short period (~3.5 day) spectroscopic binary of two nearly identical stars. Surprisingly, the two stars, though differing in effective temperature by only ~250 K and having a mass ratio of 0.91, show very different Li line equivalent widths. A Li 6707 Angstrom line is only detected from the primary star, and it is weak. This star is therefore likely to be older than 1 Gyr. If so, the large amount of hot circumbinary dust must be from a very large and recent, but very late evolutionarily, collision of planetesimals.Comment: Accepted to ApJ Letters, with corrected typos and added info on Li equivalent width

The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MEGaSaURA) I: The Sample and the Spectra

We introduce Project MEGaSaURA: The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises medium-resolution, rest-frame ultraviolet spectroscopy of N=15 bright gravitationally lensed galaxies at redshifts of 1.68$<$z$<$3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range $3200 < \lambda_o < 8280$ \AA ; the average spectral resolving power is R=3300. The median spectrum has a signal-to-noise ratio of $SNR=21$ per resolution element at 5000 \AA . As such, the MEGaSaURA spectra have superior signal-to-noise-ratio and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum. We provide the MEGaSaURA spectra to the astronomical community through a data release.Comment: Resubmitted to AAS Journals. Data release will accompany journal publication. v2 addresses minor comments from refere